The 40th London Marathon will show what the city can achieve when communities come together, event director Hugh Brasher said.
Mr Brasher, whose father Chris founded the event with John Disley in 1981, said the race is not just about people running 26.2 miles: “It’s about London coming together, showing what London can do when we support each other.”
Speaking at the launch of the 2020 Virgin Money London Marathon at Tower Bridge, he said runners “will be floating on a sea of positivity”, adding: “For so many people it’s the greatest day of your life.”
Among those praised at the launch event were the 10 Ever Presents who have run every London Marathon, including the oldest member Ken Jones, 86, from Strabane, Northern Ireland, who told the audience: “It’s a great privilege to be here with all these runners and all my friends.”
The youngest, Chris Finill, 61, from Cranleigh in Surrey, will attempt to break three hours again this year which would mean he has run under three hours in marathons in six different decades.
“I’ll give it my best shot,” said Mr Finill who has run 37 of his 39 London Marathons under three hours.
Mr Brasher earlier presented all the Ever Presents with Spirit of the London Marathon medals.
A medal was also given to British Transport Police officer Leon McLeod who gave lifesaving treatment to victims at the scene of the 2017 terror attacks in London Bridge after he was one of the first responders.
He ran the London Marathon last year and raised thousands of pounds for the PTSD999 charity which helped him to deal with post-traumatic stress disorder.
BBC broadcaster Sophie Raworth, who hosted the event at the bridge which marks the race’s halfway point, said the London Marathon has changed her life.
She first ran it in 2011 but blacked out after 24 miles and woke up “to find someone taking my temperature internally in the middle of a crowd”.
She went on to finish the race and has now completed all six World Marathon Majors, the Marathon des Sables and will run in an England vest at the Fleet half marathon in March.
“I got introduced to running and it’s all their fault,” she said.
Raworth said the London Marathon was special because “however fast you are, you could be beaten by Spider-Man”.
She added: “I have been beaten by a wooden spoon.”
Among the famous faces at the launch were former England footballers Danny Mills, Stephen Warnock and Karen Carney, Olympic champion cyclist Joanna Rowsell Shand, gold medal winning rower turned Strictly Come Dancing competitor James Cracknell, broadcaster Jenni Falconer and EastEnders actress Tanya Franks. All plan to run on April 26.
Raworth said this year’s London Marathon, which will see Kenenisa Bekele against Eliud Kipchoge in the men’s race, will be “extraordinary” and she would like to be watching it on television.
Bekele ran the second fastest marathon time in history in Berlin in September, two seconds over Kipchoge’s official world record of two hours, one minute and 39 seconds. Kipchoge’s sub-two-hour marathon in Vienna in October is not recognised by World Athletics.
Mr Brasher said: “It’s going to be absolutely spine chilling.”
The women’s race will also be dramatic as the top British runners compete for two places at this summer’s Tokyo Olympics.