A juvenile minke whale that became stranded in the River Thames has been put down.
Hundreds of people gathered along riverbanks in south-west London after the whale was first spotted on Sunday.
It was first freed from Richmond Lock but became stranded a second time in Teddington.
Rescuers earlier said the mammal's condition had deteriorated "rapidly" and a vet team had been working to "end its suffering".
A vet from the Zoological Society of London administered the injection shortly after 18:00.
The whale is now being moved and a post-mortem examination is due to be carried out.
The minke, which measured between 3m (10ft) and 4m (13ft), was first spotted near Barnes Bridge and became stranded on Richmond Lock's boat rollers at about 19:00 BST on Sunday.
RNLI teams managed to remove it but it escaped as it was being towed and was seen swimming between Richmond and Teddington earlier on Monday before becoming stuck.
British Divers Marine Life Rescue previously said the whale had been having difficulty swimming as its "strength reserves seem to be compromised".
They said a veterinary team had been "on stand by to euthanise the animal to end its suffering".
Julia Cable, national co-ordinator of the BDMLR, said the mammal had not been "acting the way it did last night" and had "basically lost any energy that it had left in it".
She added: "It's also got another stranding injury which along with ones from yesterday all adds up really."
Dan Jarvis, also of BDMLR, said: "It's for a very good reason they've come ashore. Sometimes it is by accident, they do get stranded, but usually sadly it is the case that they're already seriously ill or badly injured.
"And there's not a great deal we can do in that situation."
Liz Sandeman, co-founder of Marine Connection, said the whale's welfare had to be considered as it was not just a case of getting it back to sea if it was a young animal.
"It wouldn't know how to feed. It learns everything from its mother - how to navigate, how to hunt," she said.
Minke whales are the smallest of the great whales, growing to about 33ft (10m), and are usually found throughout the northern Atlantic and Pacific Oceans.
Their range extends from the ice edge in the Arctic during the summer to near the equator during winter.