Ken Livingstone's past life experimenting on live animals has been detailed for the first time by two of his former colleagues who have described how he conducted tests on mice, rats, rabbits, sheep and goats.

The London mayor, known for his love of newts, spent two years helping to carry out procedures on animals at a laboratory in Sutton, south London.

The tests were performed at the Chester Beatty research centre, now part of the Institute of Cancer Research, in the late 1960s, when Livingstone was in his twenties. He worked as a laboratory technician at “X block” on approved medical research.

Livingstone was responsible for cultivating tumours in the smaller rodents by injecting them with cancer cells or car-cinogenic substances. Sheep were also given cancer in order to study their lymphatic systems.

All the animals were then either given experimental treatments to fight cancer or simply observed to see how their own immune systems attempted to combat the disease.

Among other experiments carried out at X block was a test in which researchers crushed or amputated the legs of mice to see how it caused tumours to spread. It’s not known whether Livingstone participated in or knew about such experiments.

Dr Chris Grant, who was researching his doctorate at the centre at the time, said Livingstone worked as an assistant to him and other researchers and added that he was “a confident animal technician” who enjoyed his job. “He would be responsible for setting up the cages, putting the right amount of mice in there and injecting them with the right amount of whatever I gave him,” Grant said.

“I think he liked his job. I think he used to play with the odd mouse and stuff like that. You can get people who get a bit callous after a while but I never saw that in him.”

Grant’s brother Roger also worked alongside Livingstone, helping to clean out the animals’ cages. “He was a bit of a sensitive soul,” he said.

“There were some times when the rats did seem to have tumours that were really developed. Ken maybe didn’t like that and I think he was right, too.”

Although Livingstone made noreference to his experience as an animal tester in his autobiography, in another book, Citizen Ken by John Carvel, which was published in the early 1980s, his time at the Chester Beatty is mentioned.

According to the book, Livingstone, who began working for the research centre in 1962, when he was 17, moving to X block about six years later, is said to have become distressed at the level of suffering endured by some of the animals and remonstrated with the scientists.

Grant, 63, who now runs a company in California that sells antibodies, said although some of the experiments were “pretty horrific” he did not recollect Livingstone ever complaining.

“I don’t remember him dancing up and down saying, ‘I’m not going to stand for this’,” Grant said. “If something like that had caused trouble I’m certain I would have heard about it and I don’t recollect it.” Both Grant and his brother said they liked Livingstone, but added that he did annoy others with his “constant talking about politics”.

“I can remember people getting impatient with him but that was because he insisted on talking almost communist propaganda all the time,” said Grant. “It did get tiresome.”

Roger Grant, 61, said: “He was such a political animal, many times he would start a discussion on his social ideology and you would say, ‘No, Ken, you are living in fantasy land’, and after a while people would just start walking away.

“He was a nice bloke to work with, though, he had a good sense of humour.”

Apart from talking about his left-wing creed, the only other topic that was of consistent interest to Livingstone was his collection of pet reptiles, which he kept at his parents’ home in nearby Norwood. “When he wasn’t talking about politics he was talking about lizards and snakes,” Grant said.

Livingstone, is up for reelection in May. A spokeswoman from his campaign said: “Some parts of the media seem to wish to talk about anything other than the actual political issues at stake.”

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