With coronavirus restrictions preventing the mass participation event taking place on the London Marathon course, 45,000 runners are taking part remotely on Sunday.
Here are the stories of five groups of runners and what is motivating them.
Amie and Yvette Mclean Amie and Yvette are running for their brother and son Ethan who suffers from Duchenne Muscular Dystrophy.
Eleven-year-old Ethan is no longer able to walk because of the genetic muscle-wasting disease.
They will complete the marathon distance on a five-mile stretch of beach on the north coast of Northern Ireland, called Benone Strand.
Ethan loves spending time on the beach and it is where the family have enjoyed escaping to after shielding during the pandemic.
Simon Gallo Simon spent three months battling Covid-19 with his recovery complicated by an auto-immune disease which almost cost him his lower right leg.
He was treated at Ipswich Hospital and to thank them for their care and treatment, he will run laps around the hospital, raising money for both the National Health Service and National Society for the Prevention of Cruelty to Children (NSPCC).
Sunday will be his 25th consecutive London Marathon.
Tina Fallon June and Tina Fallon, the mother and sister of former British Judo player Craig Fallon will be walking 26.
2 miles for Mind - the mental health charity.
Craig, who won a world title in 2005 and is widely regarded as Britain's best ever judoka, died in 2019, with the coroner recording a verdict of suicide.
His mother and sister will finish their 26.
2 miles at the Shropshire beauty spot where he took his own life, hoping to raise awareness of mental health.
Maqsood Sheikh Maqsood Sheikh from Bradford should have been marking his 50th year by taking part in the 40th London Marathon and his first.
He planned to run raise money for the Royal National Institute of Blind People (RNIB).
Maqsood, who works for the sight-loss charity as a Regional Campaigns Officer, was born with optic atrophy.
It is a condition which can cause blurred vision and impact peripheral vision.
His friend and guide runner, Donna Siberry suggested they run the marathon together and they have kept training through the summer to keep fit for the rearranged date.
They will be completing 26.
2 miles along the Rochdale Canal, starting in Friendly, Sowerby Bridge and running to Summit near Littleborough, returning and finishing in Luddendenfoot.
And they hope to be on the start line in London in 2021.
Bobby and John Bobby and John are British Army soldiers, originally from north-east England, now stationed in London.
They are running in the capital to raise money for Veterans in Crisis, a Sunderland-based charity that works with former service men and women.
The charity is raising money to safeguard its future after the building it is based in was put up for sale.
Bobby and John will be on guard the day after the marathon at Buckingham Palace and St James' Palace, looking out at where the elite fields will have raced.