Edwin Timwell tries to manoeuvre a northern bottlenose whale away from the tidal shore of the Thames near Battersea Bridge in London, Friday, Jan. 20. (AP Photo/Sang Tan)

Londoners crowded along the River Thames on Friday to catch a rare glimpse of a large whale swimming past Parliament and Big Ben.

Measuring about five to six metres, the northern bottlenose whale swam under Westminster Bridge, coming close to the banks of the Thames. Followed closely by a police boat, the whale nearly beached itself and appeared to get stuck a couple of times.

Rescue officials rushed to push the seven-tonne mammal into deeper water as television crews broadcast the events on television.

Marine experts speculated the whale was lost or ill and became confused.

Vets remained on standby as emergency workers waited for special equipment to try to redirect the whale downstream in the tidal waterway. The whale already cut itself and bled after crashing into an empty boat, said a BBC report.

This type of whale is usually found in cold, deep North Atlantic water and rarely ventures into the English Channel. London's Natural History Museum said it's the first instance of a northern bottlenose in the river since 1913.