The morning of Tuesday, 22 January 2019 is etched on my memory as if it were yesterday.

I dismissed the link. Surely there must be lots of planes making that journey all the time?

But within the hour, BBC Wales football correspondent Rob Phillips reported Cardiff were "seeking clarification" about the missing plane and there was "genuine concern" at the club.

Argentine Emiliano Sala had signed for Cardiff just three days earlier in a club record £15m transfer from FC Nantes. As that Tuesday unfolded, instead of welcoming their much-anticipated new striker to a training session, they were instead facing a barrage of enquiries from the world's media about an unfolding tragedy.

It was soon confirmed Sala was on the Piper Malibu plane - piloted, it would emerge over the next 48 hours, by David Ibbotson - when it disappeared from radar north of the Channel Islands, just over an hour after take-off from Nantes Atlantique Airport. At that time, there were no signs of wreckage.

Few stories I've covered as a journalist captured the public's attention the way this one seemed to.

Sala was a prolific striker revered by Nantes supporters. For Cardiff fans he was the longed-for talismanic figure who might help save their struggling team. He was a talented, adored young footballer tragically lost just as his Premier League career was about to begin.

The level of interest in the story was such that my investigations team colleague Kayley Thomas and I were asked to start looking into the circumstances around the flight. The result is the BBC Sounds and BBC Radio Wales podcast series: Transfer: The Emiliano Sala Story. You can listen to episodes here.

As we began researching, it became clear this was a story that wouldn't be leaving the headlines any time soon.

And as the fourth anniversary of the crash approaches, so it has proved.

When Emiliano Sala was born, a month prematurely, on 31 October 1990, his parents were warned he might never be able to run because of the effect on his respiratory system. But he exceeded all expectations, growing into a healthy and energetic child, close to his younger siblings Romina and Dario.

At the age of four, Sala's mother Mercedes Taffarel took him to a local football club, San Martin de Progreso, initially wearing a pair of trainers as the family couldn't afford football boots.

His passion for the sport flourished and when football scouts spotted his potential aged 15 he decided to move 200km away to train with an Argentine football college in San Francisco, in Cordoba province.

"He told me that I should let him go; that all he wanted in his life was to kick a ball and if I didn't let him, I would be killing him inside," Mercedes said in a poignant statement to his inquest earlier this year.

San Francisco's connections with European clubs helped Sala pursue his dream of playing the game at a higher level. Stints with teams in Spain, Portugal and France followed before he was signed by FC Nantes in 2015. There he scored 48 goals in 133 appearances over three seasons, making him a fan favourite - and also a target for management to sell on.

When Cardiff's manager at the time, Neil Warnock, saw him play against Marseille at the beginning of December 2018 - scoring one goal and setting up another in a 3-2 Nantes victory - he knew he'd found his new striker.

Negotiations began - led by agent Mark McKay, whose company Mercato Sports had the mandate from Nantes to sell Sala. A chain of events that would lead to catastrophe was set in motion.

When Kayley and I visited Nantes for the first time in December 2019, as the first anniversary of Sala's death approached, it was clear from conversations with his friends that he was initially unsure about the move to Cardiff.

Marie-Jeanne Munos Castelleanos welcomed us into her cosy bungalow, plying us with coffee and chocolates and chatting away warmly.

Describing herself variously as a surrogate mother or mental coach to Sala, she showed us the many photographs and other mementoes of their friendship. She generously shared voice messages he'd sent her in which he alluded to reservations about the transfer.

"From the start of it all, he hadn't properly decided whether he was even going to Cardiff," Marie-Jeanne told us.

"His mum wanted him to go, but he was worried because he was used to life in Nantes, he had his routine and all that.

"He'd be going to another country, where he didn't know the language. He was a bit worried about it."

Mercedes' statement to the inquest into her son's death also referred to him feeling under pressure about the move, which she said was pursued by the owner of Nantes, Waldemar Kita, for financial reasons "against the wishes of coaching staff and fans".

The transfer fee of £15m was a record for both Nantes and Cardiff.

Sala lived in the small town of Carquefou - a drive of 40 minutes or so outside Nantes. Locals were well used to seeing him as he went about his business; shopping in the supermarket, having a drink or meal in his favourite bar, getting a haircut or worshipping in the local church.

The picture that emerged during our visit was far removed from the typical image of a star footballer. Here was someone who spent much of his free time walking his rescue dog, Nala, or hanging out with hairdresser Jean-Philippe Roussel and his wife Lydie, who had become close friends.

Roussel says: "He knew that leaving Nantes could be a good career move, but was he in favour going to Cardiff? No… he was being pushed out, to be honest."

Nantes told the Transfer podcast series that Sala chose to leave of his own free will "after many great years" there.

Nantes supporter Louis Chene, who lives in the centre of Carquefou, would sometimes bump into Sala and chat to him about the club's fortunes. He recalls Sala going around the town saying goodbye to everyone when he knew he was leaving.

"He went down the street and at every little shop he knew, he went in," Chene says. "He wanted to say a personal goodbye to people."

Frederic Happe, a journalist with Agence France Presse who had followed Sala's career in France, says: "He really was the most likeable person you could imagine. He was one of the few players who asked you how you were when you came into the conference room: 'Hi chaps, how are you doing?' Small details, things players at a certain level tend to forget."

These small but telling details gave us a rare and invaluable insight into a life some would be quick to dismiss as privileged but which we came to realise was at the mercy of the whims of others; be it agents seeking new transfer targets, or football club owners seizing a chance to make money from their star striker.

The very last photograph Sala posted on his Instagram page - taken just hours before the crash - is captioned: 'La Ultima Ciao' (The Last Goodbye).

Sala is smiling with an arm around one team-mate as the rest of the Nantes side cluster around. Among them is his best friend at the club, Nicolas Pallois, who with his wife would drive him to the airport that evening and, some weeks later, travel to Argentina for his funeral.

A pervading sense of reluctance hangs over Sala's story - from those last images of him bidding farewell to the club and community he's happy in, bound for a new job he never applied for, to the poignant voice message he sent to his closest friends back in Argentina from the tiny Piper Malibu as it taxied on runway 3 of Nantes Atlantique Airport before take-off.

"I'm on the plane that looks like it's falling apart," he says as the engine can be heard in the background. "I'm heading to Cardiff because I start training with the new team tomorrow afternoon.

"If you don't hear from me in the next hour and a half, I don't know if somebody will look for me, because they won't find me.

"Man, I'm scared."

This wasn't Sala's first time on the Piper Malibu.

In an earlier message, after landing in Nantes on the journey out from Cardiff two days earlier, he'd described it as a "coucou" - French slang for a rickety old plane.

We now know, from a recording we obtained of a phone call Ibbotson made to a friend following that flight, that he, too, had concerns about the "dodgy" aircraft.

The 59-year-old gas fitter with a passion for flying had been asked to take Sala to France and back by David Henderson, who operated the Piper Malibu plane on behalf of its owner but couldn't take on the job himself as he was away in Paris with his wife.

The private flight was arranged by Willie McKay, the former football agent helping his son Mark broker the transfer deal.

Willie McKay later told the BBC: "I was just thinking about getting the boy back home. We just tried to help."

For their part, Cardiff City said they had offered Sala a commercial flight back to Nantes, via Paris.

McKay said he trusted Henderson and "had no reason not to".

But private pilot Ibbotson had no licence to carry paying passengers and was not qualified to fly legally at night. In addition, his rating to pilot the single-engine Piper Malibu aircraft had expired two months earlier.

In a conversation with a pilot friend the day before the fatal flight, he's heard saying he normally stowed his lifejacket between the plane seats but "tomorrow I'll be wearing my lifejacket, that's for sure".

Winding up the call he says: "You know if anything did happen… it might be your last chance to have a good old chat with me and a good old moan with me."

His comments - made in a jovial tone but revealing underlying unease - eerily echoed Sala's reservations.

Among the issues on their flight from Cardiff to Nantes were a loud bang - the source of which was never identified - a "low mist" in the cockpit and the stall warning device randomly going off.

On landing, Ibbotson found the left brake pedal wasn't working when he tried to turn off the runway.

"Why didn't Sala just refuse to get back on it?" is a question many have asked since.

The language barrier - Ibbotson speaking no Spanish or French, and Sala no English - can't have helped.

But get back on it he did, and at 19:15 in the evening of 21 January, flight N264DB soared into the night sky out of Nantes, heading north towards the Channel.

Just over an hour later, the plane lost radar contact north-west of Guernsey, about four minutes after Ibbotson's final contact with Jersey air traffic control.

Air accident investigators concluded the pilot lost control as he descended to avoid cloud. The plane crashed into the sea at an estimated 270mph (434km/h), starting to break up as it descended with a G-force exceeding anything experienced by fighter pilots.

The drive and determination of shipwreck hunter David Mearns turned out to be pivotal to determining the cause of the crash.

Without his involvement it's likely the wreckage of the plane - and Sala's body - would never have been found. Ibbotson's body has not been found.

We first met Mearns back in summer 2019. His passion was evident as he told us of his desire to spare families of those lost in such accidents the "double tragedy" of not having a body to bury.

"You're doing this on behalf of them. You volunteered and gave your time to do this, and you want to find him for them," he said.

He recalled telling Sala's mother: "I'll find him… I'll find the plane and hopefully he's there."

Mearns drove the search for the wreckage on behalf of the Sala family after hundreds of thousands of pounds were raised through a fundraising campaign.

His survey vessel found the plane's resting place on the seabed in a joint mission with the Air Accidents Investigation Branch in early February 2019.

A few days later, a painstaking operation by a specialist ROV (remotely operated vehicle) team working in shifts managed to recover Sala's body, which had become trapped in the wreckage, and it was brought ashore at Portland in Dorset.

Mearns later returned to the crash site on behalf of the Ibbotson family, but found no trace of the pilot.

It was a late hunch on the part of the home office pathologist in the case, Dr Basil Purdue, that led to toxicological testing being done on Sala's body and the surprise discovery of dangerously high carbon monoxide levels in his blood.

They found that Sala would have been deeply unconscious from carbon monoxide poisoning - probably leaking from the plane's exhaust system - and that Ibbotson would likely have been affected too, though to a lesser degree.

Ibbotson's final communication with air traffic control was lucid and he was actively flying the plane in its final moments, leading investigators to believe a dramatic leak of carbon monoxide into the cabin must have occurred in those ensuing four minutes before the crash.

This shifted the focus of the investigation from pilot error towards the condition of the plane - and those responsible for its maintenance.

Investigations by Dorset Police and the Civil Aviation Authority followed, and in June 2019 plane operator Henderson was arrested at his home in York.

At Cardiff Crown Court in October 2021, Henderson pleaded guilty to trying to arrange a flight for a passenger without permission or authorisation, and was convicted after a trial of recklessly endangering the safety of an aircraft in the way he'd organised the flight for Willie McKay.

Sentencing him to 18 months' imprisonment, the judge in the case said Henderson had a "cavalier attitude" to safety regulations, that he was motivated by profit and that messaging between him and Ibbotson in the run-up to the flight revealed his "lurking doubt" that the amateur pilot wasn't up to the job.

In February 2022, the inquest into Sala's death finally began in Bournemouth.

His younger brother Dario attended in person for the first week and then remotely via video link, an interpreter always at his side.

Speaking to the BBC's Transfer podcast series, he recalled the happy childhood spent with his brother and spoke of the impact of his death.

"It's affected us so much," he said. "He had a very important role within the family. We were always very close, now it's hard looking to the future knowing he's not there if I want to ask him something or get his advice… it's not easy."

In a statement read out after the inquest, Sala family lawyer Daniel Machover said: "This inquest has exposed the complex facts leading to Emiliano's untimely death. It has shone a bright light on many of the missed opportunities in the worlds of football and aviation to prevent his tragic death."

The family welcomed the coroner's decision to issue a Prevention of Future Deaths report highlighting her concerns about the safety issues arising from the case, adding: "No family should have to go through grief from a similar avoidable accident."

Radar contact was lost when the aircraft was 22 nautical miles (40 km) north-north-west of Guernsey

'Money with a Capital M' was the title we gave one episode of the podcast series. It references a quote from the Sala family barrister about an email Willie McKay sent to Sala, persuading him to consider Cardiff City's offer, in which the 'm' of 'money' was capitalised at every mention.

But it might have applied to almost any aspect of this story, where money was seemingly being made from him at every turn: as a footballing asset, as a passenger, as a much-needed goalscorer to keep a struggling club in the Premier League with all the financial benefits that brings.

In September 2019, football's governing body Fifa ruled Cardiff should pay Nantes the first £5m instalment of the transfer fee or face a three-window transfer ban.

Cardiff appealed to the Court of Arbitration for Sport (Cas) in Switzerland, which in August 2022 upheld Fifa's ruling, confirming Sala was a Cardiff player at the time of his death.

Cardiff had argued the transfer wasn't complete - partly because Sala wasn't yet registered as a Premier League player. But Cas agreed with Fifa; because Sala had been registered with the Welsh Football Association as a Cardiff player, the transfer was complete.

The full judgement from Cas also revealed the Premier League initially rejected Sala's registration because of mistakes Cardiff had made in his employment contract.

As a result, while Sala was in the Piper Malibu flying to Cardiff, his agent Meissa N'Diaye was involved in amending his contract with the club. The new paperwork was finalised just eight minutes before the plane disappeared from radar.

Cardiff have subsequently challenged the Cas judgement by lodging a further appeal to the Swiss Federal Court. If this fails, the club has said it will take civil action against those involved in organising the flight "for damages to recover its losses. This will include FC Nantes, and its agents."

A statement released following the Cas judgment added: "All our thoughts must continue to be with Emiliano's family, who are now supported financially by the trust the club put in place for them."

Appearing on the Transfer podcast series, the Guardian's investigations reporter David Conn said: "Whatever the technical rights are, whatever the legal niceties are, it's quite a stain on football's image, reputation and honour that this unseemly row has been going on for so long after a wonderful young man suffered this horrendous death."

Almost four years on, the impact of Sala's death continues to ripple out.

His father Horacio died from a heart attack three months after the crash, aged 58. He was separated from Sala's mother and living with a new partner. Friends said he was heartbroken and struggling to come to terms with the loss of his son.

At the inquest into Sala's death, his mother Mercedes said the family miss him "each day like the first day".

She added: "No-one can bring Emi back to us, but we ask for justice, so Emi can rest in peace and give us a little peace of mind knowing that we did everything we could so that similar deaths are prevented in future."

Sala's sister Romina, a new mother herself when she travelled to the UK to urge the authorities to keep searching for her brother, has struggled emotionally since the tragedy.

Meanwhile, civil actions are ongoing on behalf of the Sala family against a number of parties.

The streets of Progreso were packed when 'El Emi' - as the local boy made good was known there - came home to be laid to rest.

Now he watches over them from the mural painted by Argentine artist Gabriel Griffa at his old club St Martin de Progreso, whose home ground has since been renamed the Emiliano Sala Stadium.

In spring 2022 the artist travelled to Carquefou to paint another mural of Emiliano there, organised by Marie-Jeanne, the Roussels and other friends and fans.

Two towns, many hundreds of miles apart but forever connected by this talented, popular and well-loved young man who will never be forgotten.