A man carrying a 99p toy gun claims he was Tasered nine times by police whilst sat on a train.
The victim, Justice Livingston, said he was Tasered three times in the head and four times in the leg on a carriage at Norwood Junction.
Officers were deployed following a report that a man had boarded the train with a firearm.
Having been approached by police on the train, Livingston said he was ordered to open his briefcase, which he did.
“They saw the toy gun. Then a male police officer opened fire with a gun which jammed.”
Scotland Yard denies that any firearm other than a Taser was used.
According to Livingstone, the officers then “jumped” at him, firing the Taser four times at his chest. When that had no affect, they grabbed him, pinned him down and fired three more charges into the back of his head.
"They tied my legs and took me off the train to the platform," he said.
According to Livingstone, he was taken to Victoria Police Station in London, where officers apparently mocked his attire – a black hat and a long black coat.
Having refused access to a lawyer, he was taken to Bethlem Royal hospital in Beckenham where he was sectioned under the Mental Health Act but was released later released on appeal.
According to police, attempts to restrain the man failed so they used a Taser.
A spokesman said: "When police arrived the man had boarded a train which had been held at the station. Officers boarded the train and made their way through the carriages to the male suspect who had his hands in his pockets.
"The suspect moved forward towards the officers whilst shouting and refused to remove his hands from his pockets. Attempts by the officers to physically restrain him failed so they deployed Taser.
"The man was Tasered a number of times but this seemed to have no effect. Eventually officers were able to physically restrain the man and he was removed from the train and into the custody of British Transport Police."
Police said they were alerted following reports that a man was waving a gun on a platform.
Livingstone said he would be making a formal complaint.
On Tuesday, Bernard Hogan-Howe, commissioner of the Metropolitan Police, argued that all police cars should be routinely armed with Tasers.