VIDEO: Man races underground tube train
James Heptonstall's plan was to jump off a Tube train at one station, cover 380 metres to the next station, and make it there in time to jump back onto the same train.
He and his friend Noel Carroll took the Circle Line train to London's Mansion House station.
As you'll see in the video, 30-year-old Heptonstall leaps off the train at Mansion House, then makes a dash for it and hopes to arrive at Cannon Street station in time to re-join his friend.
Does he succeed in the near-impossible?
You'll have to watch the video and follow his crazy sprint step by step to find out!