The river Thames is the longest and most famous river to flow entirely though England. It’s a place where a large body of fresh water meets with an even larger body of salt water, and thus it’s home to a tremendous variety of plants and animals – who lurk just beneath the surface, and along the bed of the river.

Today, you’ll be able to see much of modern London while floating along a London river cruise. If you’re feeling especially enamoured with the river, you might even decide to hold a major event here – among the best London wedding reception venues are the ones that float down its major river.

It’s also a river that’s had a tremendous impact on human history, with settlers here having used the river extensively as a port. Roman conquerors would use it to ferry supplies to and from the ports of the Mediterranean, and for subsequent British Empires, it would be a trading gateway into the rest of the world.

The recent history of the river has seen it host a rather unusual life-form. On the 20th January 2006, a bottlenose whale found its way into the river, where it died. The whale caused quite a stir when it arrived, closing the waterway for the first time since the funeral of Winston Churchill. Ten years later, the event was commemorated in a march from the Natural History Museum and the Battersea park beach. This was a rather peculiar affair, with whale-song being played over miniature speakers attached to a bicycle.

So how did this bizarre and tragic series of events come to pass? Let’s investigate.

What is a bottlenose whale?

The bottlenose whale was first described in 1770 by a pastor and naturalist named Johann Reinhold Forster. He based his name of choice on previous descriptions of what he assumed to be the same animal – the whale, like its cousin the bottlenose dolphin, comes with a nose (or beak) that protrudes slightly from the front of its head. That said, the whale is far larger than the dolphin, measuring around ten metres long and being considerably chunkier.

These whales spend much of their time diving to considerable depths in search of food – but they’re also known to spend some time near the surface, where they play and rest. They’re found in the North Atlantic, where they number around 10,000.

So what persuaded this particular whale to make the apparently arduous trip into the mouth of the Thames? There are several competing theories. One holds that the whale lost its way after becoming ill. Sometimes, infections can interfere with a whale’s ability to properly navigate. Hearing damage, thanks to military sonar use, was one popular theory – but the autopsy didn’t show any damage to the animal’s ears. Another unlikely theory is that the whale ventured up the Thames in search of food, chasing after a shoal of fish – but whales of this sort tend to subsist on squid rather than fish.

The likeliest explanation, and the one performed by the experts who carried out the post-mortem, is that the whale simply got lost. Rather than taking the longer route along the North Sea to return to the Atlantic and its usual feeding grounds, the whale instead ventured down the Thames. As for the cause of death, the veterinarians carrying out the post-mortem, led by Paul Jepson, concluded that muscle damage as a result of contact with the riverbed, dehydration and ultimately kidney failure had killed the whale.

The events themselves

After members of the public had spent the day of the 20th trying to coax the whale back to deep water, without success, it was decided that the whale had to be assisted back to its home. Whales of this sort are accustomed to depths of hundreds of metres, and the thames is only a few metres deep. With blood visible from repeated scrapes against the riverbed, the British Divers Marine Life Rescue decided to act. With help from the police and the port authority, they beached the whale on a sandbank and stretchered her out of the water. Getting her back to the sea, however, proved a task too far – and the animal would go into convulsions and die just after 7pm on the 21st of January.

The story of the whale that visited London has since inspired a raft of musical and literary tributes. You can now visit the famous whale’s skeleton during your trip to the capital – it’s preserved behind glass at the Natural History Museum.