Peter Tatchell, the human rights campaigner, revealed yesterday that he has brain damage from being beaten first by Robert Mugabe's bodyguards and later by Russian neo-Nazis.
Mr Tatchell, 57, said his condition was so severe that he has stood down from his role as Green Party candidate in Oxford East and put his political activity on hold after doctors advised rest. He said yesterday that it was a "painful, distressing decision", but added: "You haven't heard the last of me yet."
In 2001, he attempted to make a citizen's arrest when Mr Mugabe was in Brussels. He got as far as saying that he was arresting the Zimbabwean President for civil-rights abuse when the bodyguards set upon him. They attacked him in a hotel lobby and followed him out into the street, where they threatened to kill him and attacked him twice more, knocking him unconscious. For several days he suffered from numbness and some paralysis down his left side, which doctors identified as symptoms of severe concussion.
In May 2007, Mr Tatchell joined a Gay Pride march in Moscow, which was attacked by a right-wing gang while the police looked on. He was punched in the face, thrown to the ground, and kicked by youths shouting "sodomy" and "sodomite". The punch has permanently affected the vision in his right eye. "But in some ways I was lucky, because an environmental camp was attacked later by people who I was told were from the same group. They killed one person and put 15 in hospital," he said.
His injuries were compounded on a campaign trip for the Greens in Devon, in July, when the campaign bus braked suddenly and he was thrown forward, hitting his head by a metal rail.
"Following the Moscow assault, I never rested and recuperated," said Mr Tatchell. "I carried on campaigning, with a very heavy schedule of commitments in Oxford East. After several months, I was severely exhausted. This stress and exhaustion probably intensified the damage and thwarted my recovery. I have postponed making this announcement for several months, in the hope that I might get better and be able to carry on as the Green candidate. Unfortunately, my condition has not improved. If anything, it is worse. I am slower, I make more mistakes and I get tired very easily.
"There is, however, a glimmer of hope for the future. The medical advice is that if I slow down and reduce my workload, my condition may improve in a year or so. On the downside, I am unlikely to ever recover fully. Some of the damage is probably permanent.
"I don't regret a thing. Getting a thrashing and brain injuries was not what I had expected or wanted, but I was aware of the risks. Taking risks is sometimes necessary, in order to challenge injustice. My beatings had the positive effect of helping draw international attention to the violent, repressive nature of the Russian and Zimbabwean regimes. I'm glad of that."
The Green Party will choose a new parliamentary candidate in Oxford East in January. The party has never had an MP and was not likely to have won Oxford East. In 2005 it came fourth with 4.3 per cent of the vote but has since done well in local elections.
Losing a high-profile candidate is, however, a blow to a party which is hoping to win a seat in the Commons for the first time at the next election, when its leader, Caroline Lucas, will contest the Brighton Pavilion constituency.
Mr Tatchell first became nationally known when he was Labour candidate in a highly publicised by-election in Bermondsey in 1983. It was one of the worst defeats Labour has ever suffered, when a previously solid seat was taken by the Liberal Democrats, but it left many people feeling that Mr Tatchell personally had suffered unjustified abuse for being gay.