The London Marathon could accommodate more than 100,000 participants in 2027 under proposals to extend the iconic endurance event across a two-day format.
Organizers are exploring a significant expansion of the annual race, one of the capital's premier sporting fixtures, through what the Guardian reports has been internally referred to as the Double London Marathon initiative.
The proposed structure would distribute 50,000 amateur runners across 24 April, with an additional 50,000 competing the following day. Elite competition fields may similarly be divided across the weekend.
Such an expansion could generate charitable contributions exceeding £130m, building on last year's performance where 56,540 finishers collectively raised £87.3m through the 26.2-mile course. Demand remains extraordinary—this year's ballot attracted over 1m entries for the 26 April event.
While London and New York marathons regularly compete for amateur participation records, a 100,000-runner total distributed across two days would establish a benchmark unlikely to be matched by single-day events.
New London Marathon
Hugh Brasher, chief executive, told the Guardian: "The TCS London Marathon is the world's most popular marathon, and we are always exploring innovative ways to enable more people to take part and to deliver positive benefits for London.
"This work is carried out in close collaboration with our partners and stakeholders, whose support is essential in staging this incredible event in the heart of the capital each year."
Added a spokesperson for the Mayor of London: "London is the sporting capital of the world and the Mayor looks forward to working with London Marathon and partners to consider if it might be possible to host an event that will run across two days next year."
Kenya's Sabastian Sawe claimed victory in the 2025 men's elite race through London's streets, finishing ahead of compatriot Alexander Mutiso Munyao in third and Uganda's Jacob Kiplimo in second.
Ethiopia's Tigst Assefa dominated the women's competition, crossing the finish line on The Mall before Kenya's Joyciline Jepkosgei and the Netherlands' Sifan Hassan—who has since withdrawn from this year's edition.