An expert is examining the body of a bottle-nosed whale which died after becoming stranded in the River Thames.
The creature was being taken back to the sea on a barge but died despite a massive rescue effort to save it.
The huge mammal, usually found in the north Atlantic, attracted huge crowds after being spotted on Thursday.
The whale suffered muscle and breathing problems before dying on Saturday. It's hoped the tests will show why it swam out of the sea and what it died from.
Northern bottle-nosed whales
Scientific name: Hyperoodon ampullatus
Length: 7.3 - 10m
Lives in Arctic and northern Atlantic oceans
Eats squid and fish
It was first time that a bottle-nosed whale had been seen in the river since records began.
The whale was thought to be injured and it was suggested it may have swam away from the sea to die peacefully in the first place.
Tony Woodley, spokesman of the British Divers Marine Life Rescue Group who were trying to save the whale said: "It's dreadful news, but I'm afraid this is the kind of thing that can happen with these kinds of animals.
"And it's a dreadful shame. We've been throwing everything we can at this."