The lawyer David Burgess, who was also known as Sonia, died after being pushed under a Tube train. Reuters

A transsexual who pushed a distinguished lawyer in front of a train on the London Underground was cleared of murder but will face a "long prison sentence", according to the court.

Senthooran Kanagasingham, 35, was undergoing sex-change treatment when he killed solicitor David Burgess at King's Cross station in London.

Kanagasingham, of Chichele Road, Cricklewood, north London, was found guilty of manslaughter on the grounds of diminished responsibility at the Old Bailey.

He faces a long prison sentence after doctors said he no longer requires hospital treatment for paranoid schizophrenia.

The leading human rights and immigration lawyer was a cross-dresser, who had adopted the name Sonia.

She had befriended Kanagasingham, then known as Nina, and brought him to his GP just before the incident on 25 October last year, because she was worried about his mental state.

Brian Altman QC, prosecuting, said shocked rush-hour commuters had seen Kanagasingham push Sonia from the back.

A note found in Kanagasingham's rucksack said he was "broke, depressed and suffering from gender dysphoria".

Mr Altman said Burgess had built "an enviable and brilliant reputation" as a solicitor in human rights and immigration law.

"However, socially, the deceased lived as a woman and was known by friends and family as Sonia," he said.

According to Mr Altman, Sonia was "gender-variant". She did not wish to undergo gender reassignment surgery to become a woman, but to all intents and purposes lived as a woman outside her professional life.

This was "accepted and embraced" by everyone, including her three children.

"A close friend states that physically Sonia presented [herself] as a good-looking, very slim, middle-aged woman," Mr Altman said.

"Sonia was caring and generous with her time. She was tolerant of others and she habitually helped others with their problems."

He told the court that the defendant had been going through gender reassignment and would identify as a transsexual. "It had been his desire to pass completely as a woman."

Kanagasingham met Sonia at a bar and was a frequent visitor to her Soho flat, but Sonia had been wary of the defendant because she feared Nina was having hormonal treatment.

"For the purposes of this trial, he wishes to be known by his birth name and his male gender," Mr Altman said.

Shortly before her death, he added, Sonia told those close to her that Nina was becoming psychotic and "imploding".