A whale that became stranded in the River Thames has died after a massive rescue attempt to save its life.
The 18ft (5m) northern bottle-nosed whale was first spotted in the river on Friday and rescuers began an attempt to save it on Saturday morning.
But the whale died at about 1900 GMT on Saturday as rescuers transported it on a barge towards deeper water in the Thames Estuary.
It was moved after being placed in a special pontoon near Battersea Bridge.
Alan Knight, from the British Divers Marine Life Rescue (BDMLR) which led the rescue operation, said the animal died after it began to convulse while it was still on the barge.
"It has been a helter skelter ride all the way through. It is a sad end to a very long day," he said.
"Basically this is probably the right thing to happen in the end.
"If it had continued in this way we certainly wouldn't have released it.
"Perhaps this has saved that very difficult decision."
Rescuers tried to keep the whale cool as they moved it by barge
Earlier, close to Battersea Bridge, thousands of onlookers applauded as rescuers placed the whale on to a pontoon to move it from shallow water.
It was winched on to the Port of London Authority barge where it was laid on an inflatable raft functioning as a "makeshift whale mattress".
As the whale was carried downstream towards the estuary a vet administered antibiotics.
Earlier, naturalist and television presenter, Terry Nutkins, said the rescue operation was the wrong thing to do and that the animal needed space.
He told BBC Radio Five Live: "It wouldn't know what was happening, it was surrounded by boats...it would have been absolutely terrified as well as being stressed because it wouldn't be used to noises of propellers or engines.
"It was kept...like a goldfish in a bowl. So, it doesn't surprise me that it's died."
However, he later concluded he had "no doubts" the rescue operation had been the best way to try to save the whale.
"You can't leave a whale stranded in the Thames and we did the best we could," he added.
The whale, which could weigh about four tonnes, was first spotted at on Friday morning by a man on a train.
There were reports of a pod of whales in the Thames estuary earlier in the week, and it was possible that the whale had become separated from this group.
It was the first sighting of the endangered species in the Thames since records began nearly a century ago.