He may have arrived more than a week late, hampered by drought, a heat wave and a last-minute encounter with a shoal of jellyfish, but yesterday Lewis Pugh became the first person to swim the entire length of the Thames.
As he came ashore at Southend-on-Sea in Essex where the river meets the North Sea, the endurance swimmer turned eco-campaigner said that it had been the toughest ordeal of his life.
Despite having already completed long distance swims in all five oceans, and holding records in the Arctic and Antarctic, Mr Pugh said nothing could have prepared him for the challenges posed by the past 21 days.
"This challenge has proved far more difficult than I expected due to the drought and the heat wave. I just hope that my swim has brought home the message that we have to ... tackle climate change."
The highlight of the 203-mile feat came last Thursday when Mr Pugh left the river at Westminster to deliver a letter about the dangers of climate change to the Prime Minister at No 10 Downing Street. The two men spoke for several minutes.
"Going into Parliament to meet Tony Blair - I almost felt like Forrest Gump," he said.
The swim was part of a campaign by WWF to raise awareness about the perils of climate change - particularly to the polar regions where the swimmer has spent much of the last few years training.
In his letter to Tony Blair he urged the Prime Minister to visit the region and see for himself the damage that was being caused by global warming. But he said everyone had a responsibility in the battle to reduce emissions.
"What we do everyday makes a difference," he said. "Part of the reason for choosing the Thames was [that it] is being affected by climate change. Everyone has to think about what they can do to make a difference - whether on a plane or in a car."
The journey began on 17 July at Kemble, Gloucestershire. The 37-year-old Cambridge-educated lawyer was forced to run the first 20 miles because of low water levels.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies