Over 55,000 people have pre-registered their interest in the 2019 London Landmarks Half Marathon, with just 13,000 places available.
The event was created by Tommy’s, a pregnancy and baby charity, with the intention of supporting the wider charity sector.
Last year’s inaugural event raised £4.6m for 102 charities, with 10,000 runners taking part.
This year the charity has also launched a public ballot, which opens today. Those who are successful will pay a £55 entry fee for the race which will go to Tommy’s.
Over 150 charities are partners for this year’s event and people who miss out on the public ballot can sign up to run for one of them.
There are 13,000 places overall but a spokeswoman said that the organisers had decided not to make public what the split is between the public ballot and the charity places.
Lia Bowman, London Landmarks Half Marathon race director, said: “To be introducing a ballot in just our second year of operation and have over 55,000 people already interested in running the London Landmarks Half Marathon is beyond our expectations.
“We wish every prospective participant the best of luck in the ballot and remind those who aren’t successful that charity places are available for those who are unsuccessful.
“We’re thrilled that the 2018 race day was such a success and raised such an incredible amount of money for 102 wonderful charities.”