SOUTHEASTERN says it will run an extra 111 trains this Sunday, April 23 - the day of the London Marathon.
The firm has also published a series of travel tips to help people get where they need to be as easily as possible on race day.
Because trains are likely to be busier than normal, Southeastern is recommending passengers allow extra time for their journey, including spectators who are advised to take a later train and avoid the rush. London Bridge is expected to be particularly busy from 8am to 8.30am, when a large number of runners will be changing trains at the station to reach the Blackheath start line on time.
Runners can travel for free on connecting Southeastern trains from any London terminal to any start line station by showing their race number, but must buy a valid ticket for the rest of their journey.
David Wornham, passenger services director at Southeastern, said: “Anyone who wants to check which train to catch so they can get to their start line in time, or how to avoid the busiest trains on the day, can ask one of our team or check our website.
“We wish everyone taking part the best of luck and anyone cheering them on a fantastic day.”