Rescuers worked for hours to refloat it and then towed it a mile downstream. They hoped it would make its way to the ocean, but it was later spotted swimming several miles upstream.
When it became stuck again, rescuers decided the best thing to do would be to end its suffering and put it to sleep.
The size of the whale, estimated at around 4.5 meters, suggested that it was still maternally dependent. There was no sign of its mother and it was in poor nutritional health.
It's very rare for whales to come into the River Thames. The port authority said the calf would have come from the North Sea, the divide between Great Britain and Norway.