Nine teams of people are competing against each other to pull a 14-tonne, 11-and-a-half metre lifeboat, a quarter-of-a-mile, in the quickest time possible.
It is all to raise as much money as possible for the RNLI.
The lifeboat will sit on a low loader during the event, creating a massive 37 tonnes for the teams to pull through the London park.
Two men and two dogs have been saved by London's RNLI lifeboat after their canal barge got pinned against a mooring buoy in strong tide.
Crews from Victoria Embankment were called to Greenwich at 2:44pm this afternoon. The vessel - along with another which was also stuck - were towed into safe water.