Hundreds competed in the 22-mile race

The 22-mile race from Ham to Greenwich attracts competitors from as far afield as the US, Holland and Croatia, as well as from across the UK.

Vessels from dragon boats to Hawaiian war canoes compete in the race, set up by Stuart Wolff, who wanted to see more rowing boats on the Thames.

It is part of the Thames River Festival taking place this weekend.

Mr Wolff, director of the race, said: "We have got some very fit people, but we have got some relatively unfit people.

"In the same way as the marathon, we attract people that do it for fun, that do it to raise money for charity, or to get their finishing certificate - as well as out-and-out racers."

The course began in Ham, Richmond, at 1430 BST on Saturday and spectators headed to Kew, Hammersmith, Putney Bridge, Westminster and Tower Bridge to cheer on competitors.

It is part of the eighth Thames River Festival, which is expected to attract hundreds of thousands of people this weekend.

It takes place between Westminster Bridge and Tower Bridge and will feature street theatre, a treasure hunt and sandcastle competition.

Last year 300,000 people attended the free event which begins at noon and ends at 2200 BST on both days.

On Sunday, two mass choirs of 500 children and 600 adults will sing to raise money for the charity WaterAid.

London's mayor Ken Livingstone said: "The weekend celebrates the river, which has been central to the capital's history and is increasingly recognised as a place for leisure activities, for transport and for its wildlife."