A small whale has been stranded along the River Thames in south-west London.
Hundreds gathered at Richmond Lock and Weir on Sunday evening after the whale, believed to be a Minke whale - between three to four metres long, became stuck.
Videos showed it being hosed down by a man, while a vet performed a check-up at the river's edge, before the Royal National Lifeboat Institute (RNLI) arrived at the scene to cheers at around 9pm.
A witness said that "quite the crowd" watched as the attempted rescue took place.
Jake Manketo, 20, from Richmond, said: "Everyone here is just hoping they get it out.
"We couldn't believe our eyes when we first saw the poor fella, not every day something like this happens in Richmond."
The whale is said to be still alive but stuck on the lock's boat rollers, as emergency staff work to set it free.
Fire crews have also been pictured at the scene, along with the British Divers Marine Life Rescue service.
It is believed the whale was first spotted at midday a few miles up the river near Barnes Bridge.
A spokesman for the Port of London Authority, which owns and operates the lock, said: "At around 7pm on Sunday, a small whale, approximately 3-4m long, believed to be a Minke whale, became stranded at Richmond Lock and Weir.
"PLA staff have attempted to assist the whale with water along with British Divers Marine Life Rescue.
"The whale is still alive and the Metropolitan Police are working to keep the public away from the water's edge."
The spokesman added that the situation is "not good", though there is no "immediate danger" to the whale.
Minke whales are the smallest of the great whales, growing to about 10m.
They can usually be 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.
The lock is situated between Teddington and Richmond, comprising of three vertical steel gates suspended from a footbridge.