In a rare event, a whale has swum up the River Thames. Northern bottle-nosed whales are usually found in deep waters in the Atlantic.

It managed to pass the Thames Barrier and swim under many bridges including Westminster Bridge...

...before heading past the Houses of Parliament. Photo: Marine Connection

Crowds gathered on bridges across the Thames on Friday afternoon as the whale made its way upstream. Photo: Rob Fenwick

A police launch monitored the whale, with marine experts on hand in case it beached itself.

The whale swam close to shore and had to be encouraged to swim into deeper water to avoid being beached.

Its appearance attracted much attention along the river. Photo: E J May

Vets remained on standby, experts have said it does not appear to be ill, but are concerned it will get weaker and may become beached. Photo: Guy Bailey.

However, the whale crashed into an empty boat causing slight bleeding.