In her final weeks, the whale was poisoned, starved and possibly disoriented by the sonar booms of the oil industry. In the end the well-meaning attempts to save the animal may have hastened her death.

The whale, hundreds of miles from her north Atlantic hunting grounds, was so desperate for food that in her last minutes she was scavenging through the muddy shallows of the river.

After her death the animal was cut up by the government-funded cetacean strandings project and pieces sent to experts round Britain to chart her final days and establish how she died.

Preliminary results from a post–mortem earlier this year suggested dehydration and muscle and kidney damage had contributed to the whale’s death at the age of about six years. Its typical life expectancy is 40 to 50 years.

Experts have found that her last meals consisted of algae from the riverbed, part of a rubber glove worn by one of the rescuers and a small potato.

“The potato was right at the front of its stomach so it is probably something it swallowed as little as an hour before it died,” said Colin MacLeod, a marine biologist from Aberdeen University who carried out the autopsy on the whale’s stomach.

“It was probably so hungry by then it may just have seen the potato floating in the river and gone for it. The algae grows on docks and the riverbed.”

The northern bottlenose whale has seven or eight stomachs and the examination showed that her last decent meal was at least two weeks before her death. It consisted of hundreds of squid, of which only the beaks remained, lodged in the whale’s deepest stomach.

By contrast, the potato, rubber and algae was found in the stomach nearest her mouth.

An analysis of the whale’s blubber and liver by a government laboratory in Essex showed her body was laced with toxic chemicals used in paints, electronics, pesticides and detergents. The most toxic were PCBs, banned in the 1970s.

This finding suggests pollution may be reaching farther out to sea than previously thought, as northern bottlenose whales are deep-sea feeders.

The scientists’ findings — to be shown on a Channel 4 documentary this Thursday — also suggest humans played a role in the whale ending up hundreds of miles from her usual habitat.

Northern bottlenoses spend much of their time in the Norwegian Sea and the Arctic. Summer migration takes them southwest into the north Atlantic Ocean.

However, MacLeod said possible changes in water temperature caused by climate change had driven her main food, the gonatus armhook squid, southwards into the North Sea.

“If the whale then followed its natural migratory instincts to go south and west it will find all its pathways blocked by coastline,” said MacLeod.

One other theory is that the whale’s disorientation was caused by ships’ sonar.

Some have blamed the Royal Navy. But Professor Rodney Coates, an expert in marine acoustics, says the culprits may instead have been ships exploring for oil off the coast of Scot-land. They fire soundwaves at the seabed from giant guns every few seconds for weeks on end, analysing echoes for the possible presence of oil and gas.

After entering the Thames from the English Channel, the whale swam 33 miles up the river to Battersea Bridge.

When attempts to usher her back to sea failed 48 hours later, rescuers tried to lift her onto a barge to carry her out to sea. Experts now admit they may have put an unbearable strain on the whale by lifting her out of the river and losing the support of the water. The 19ft whale weighed some four tons, about the same as an African elephant.

Just one hour after being loaded onto the barge the whale died, her main organs failing through shock.

The whale is to be picked over further in the name of science. her bones will be compared with bottlenose bones from 100 years ago at the Natural History Museum in London so that changes in pollution and the marine environment can be charted.

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