The 2020 Virgin Money London Marathon has been postponed and will now take place on Sunday 4 October this year, organisers said, amid the coronavirus pandemic.
Organisers of the event, which was due to take place on April 26, said runners and charities will be contacted on Friday.
More than 40,000 people run the marathon each year while around 750,000 spectators line the streets to cheer them on.
The famous race has been rescheduled to go ahead on October 4.Hugh Brasher, event director, said: "The world is in an unprecedented situation grappling with a global pandemic of Covid-19 and public health is everyone's priority.
"We know how disappointing this news will be for so many - the runners who have trained for many months, the thousands of charities for which they are raising funds and the millions who watch the race every year.
"We are extremely grateful for all the support we have received from City Hall, the London boroughs of Greenwich, Lewisham, Southwark, Tower Hamlets, the City of Westminster and the City of London, Transport for London, the emergency services, The Royal Parks, BBC TV and many others as we worked to find an alternative date.
"The 40th race is scheduled to go ahead on Sunday October 4 2020."We know that there will be many, many questions from runners, charities and others and we ask you to please bear with us as we work through the detailed planning process to deliver the 2020 Virgin Money London Marathon on its new scheduled date.
"We will email all runners and charities today and then update them via email by the end of next week at the latest. We will also post regular updates on our website and social media channels."