A small dolphin was spotted swimming along the River Thames in the centre of London for what is thought to be only the third time in nine years.
The marine mammal spent around two hours bobbing above and below the surface close to the Palace of Westminster on Sunday.
Charlotte McGlinchey, director at Thames RIB Experience, said: “Our staff were at Embankment Pier when they saw the fin of the dolphin, but when a boat came near it, it wouldn’t come up.
“This is probably the third time we’ve had this in nine years.
“I think they are quite shy creatures anyway which is why they disappear and obviously we are quite a way up from the estuary. We just hope he gets back out there.”
In a more high profile incident, a northern bottlenose whale – dubbed the Thames Whale – was found swimming near the Albert Bridge by Battersea Park in 2006.
The whale died before it could reach the mouth of the Thames and its skeleton is on display in the Natural History Museum.
Bottlenose dolphins live in every ocean but for the Arctic and Antarctic.
In 2013, the King Seaways Ferry, which runs between Amsterdam and Newcastle, recorded an unprecedented 699 sightings inside five months, which is more than its passengers had seen in any previous year.
The Atlantic spotted dolphin lives in more tropical and temperate areas of the Atlantic such as towards the Caribbean Sea.