A dead whale has been found in the River Thames for the third time in the past two months.

The marine mammal – believed to be a minke – was spotted swimming up and down the river in London by several members of the public on Friday.

A dog-walker later found it lying motionless in shallow water near Battersea Bridge at around 9.30pm and it was later confirmed dead when a rescue team arrived.

“A whale is very unusual in the River Thames, however we have now had three in the past two months,” said Martin Garside of the Port of London Authority (PLA).

Tragic photos show beached whales Show all 15 1 /15 Tragic photos show beached whales Tragic photos show beached whales A dead sperm whale lies on Hunstanton beach in Norfolk on 5 February 2016 AFP/Getty Tragic photos show beached whales Volunteers pour buckets of water over the 80 remaining live pilot whales found stranded on remote Ocean Beach on New Zealand's southern-most Stewart island, 8 January 2003 AFP/Getty Tragic photos show beached whales Contractors clear away the body of one of the dead 48ft sperm whales that were washed-up on a beach near Gibraltar Point in Skegness, Lincolnshire in 2016 PA Tragic photos show beached whales People pass by a beached whale at the Pointe de la Torche, near Brest in France on 29 November 2011 AFP/Getty Tragic photos show beached whales A woman touches the tail of a large whale carcass on Wattamola Beach at the Royal National Park in Sydney on 25 September 2018 AFP/Getty Tragic photos show beached whales Beached humpback whale in California, 2015 AFP/Getty Tragic photos show beached whales Dead long fin pilot whales at Hamelin Bay on Australia's west coast on 23 March 2009 AFP/Getty Tragic photos show beached whales A 36ft sperm whale lies dead on the beach at Sutton Bridge, in The Wash, off the Lincolnshire coast, where it became stranded in 2004 PA Tragic photos show beached whales A female fin whale opens its mouth as it lies stranded and alive on the beach at Carlyon Bay, Cornwall on 13 August 2012 Getty Tragic photos show beached whales The lower jaw of a dead sperm whale that stranded itself on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales One of the five sperm whales that were found washed ashore on beaches near Skegness, Lincolnshire over the weekend on 25 January 2016 Getty Tragic photos show beached whales Employees at work to skin the remains of a beached 60ft whale on 25 January 2013 AFP/Getty Tragic photos show beached whales Two long-finned pilot whales are stranded on a beach in the northern French city of Calais on 2 November 2015 AFP/Getty Tragic photos show beached whales A sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales Crowds gather as a sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty

“They are all different species and there is no obvious, simple cause. Hopefully we can learn about what causes it, is it just nature or is there some external reason.’

The PLA will first move the whale to a facility in east London before handing it over to experts at the Zoological Society of London (ZSL) for a necropsy.

Around 600 cetaceans (whales, dolphins and porpoises) are found stranded around the UK coastline every year, according to the ZSL.

The society’s investigation of strandings in the UK over a 25 year period found that live strandings were the third highest cause of death after bycatch (unintentional capture by fishing industry) and infectious disease.

Hessy the humpback died after being hit by a ship while the Thames sei whale had live-stranded and also suffered from a “significant intestinal parasite infestation”.

When “Benny the Beluga” whale was spotted in the Thames in 2016 it was seen as a symbol of the threat posed by global climate change and pollution.