But the mood was buoyant and bright at Blackheath Park in south-east London as the runners prepared to begin the long haul to the finish line near Buckingham Palace.
The London Marathon route, which is lined by hundreds of thousands of spectators every year, starts in Blackheath and finishes near Buckingham Palace, passing some of the capital's most recognisable landmarks including Tower Bridge, Canary Wharf and Big Ben.