The 30-year-old had been in Queensland with Big Bash team Sydney Thunder and was only around 90 minutes away from leaving Australia on Friday to prepare for England's T20 series in the West Indies when he got the call to join the Test squad.

However, as a Covid precaution, Billings had to drive down the east coast of Australia, rather than taking a 90-minute flight.

"I thought it was a joke," Billings told Test Match Special.

"I was due to go to Brisbane airport to fly home, instead I went to Gold Coast airport to pick up a rental car and I was on my way."

Both Buttler and Bairstow have taken blows to the hand during the fourth Test in Sydney. They are awaiting the results of X-rays and neither took the field on Saturday, though they are available to bat in England's second innings.

In the absence of first-choice keeper Buttler and back-up Bairstow, Ollie Pope stood in behind the stumps.

Pope, a part-time keeper who has taken the gloves for England in one previous Test, held four catches.

England assistant coach Graham Thorpe said it was an option for Pope to keep in Hobart, though it seems more likely Billings will become the 700th man to represent England in Test cricket.

"It would be a very Sam Billings thing to do to drive nine hours to run the drinks," added Billings.

"At the age of 30, you're no spring chicken, but you do have a really good idea of where your game is at. If needed, I'm ready to go."

Billings has played 25 one-day internationals and 33 T20s since making his debut in 2015, often as back-up to Buttler and Bairstow.

He made his first England hundred in an ODI against Australia in 2020 and has been in good form for the Thunder - he left the BBL as the tournament's fourth-highest runscorer.

"I've had to bide my time in terms of an opportunity or consistent game time. I'm really enjoying my cricket, to have the chance to play and not run the drinks - I've done that too much," he said.

"I want to prove not only to myself but also to other people that I'm not just a fill-in, I am good enough to warrant a place in the side.

"If that opportunity does arise I've got no pressure on me. It's something no one really expected and I've got nothing to lose. That's a great place to be, and sometimes when you play your best cricket."

The right-hander is travelling to join an England team that will have to bat out the final day of the fourth Test in order to avoid going 4-0 down, with the Ashes already lost.

"I've been playing a lot of cricket out here, I know not in the same format, but you get confidence from game time, and that is what I've had," said Billings.

"I'm hoping to have a positive impact on and off the field and give the lads a bit of a buzz. I'm very confident with where my game is at to combat any challenge that is thrown at me."

Billings' journey began on Friday night and included an overnight stop in Coffs Harbour, near the border between Queensland and New South Wales.

His drive continued "at the crack of dawn" on Saturday morning and included a detour to the city of Newcastle "to look at the beach and water there".

"It's been quit a long drive, I'm not going to lie," said Billings. "People don't realise how big Australia is. It really is vast.

"It's been a motorway through lots of trees, hills and rivers. It's been pleasant - better than the M25."