The BBC's Jane Peel: "The Prosecution claimed the officers used unlawful force"

Richard Ilett, 34, Gary Lockwood, 33, and James Barber, 29, were cleared at the Old Bailey of killing 23-stone Irishman Richard O'Brien while he was under arrest in 1994.

Alison O'Brien: "The fight is not over"

But Mr O'Brien's widow, Alison, condemned the verdict and said she would continue to fight to protect the rights of people under arrest.

"At the end of the day they are hiding behind police uniform," she said.

'Return to normal'

Richard O'Brien died at Walworth police station

The officers left the court without commenting. A Metropolitan Police Federation spokesman criticised the Crown Prosecution Service for taking the officers to court after saying twice that it would not.

The trial followed a judicial review launched by Mr O'Brien's family after an inquest jury gave a verdict of unlawful killing.

Chief Superintendent John Godsave, of Walworth police station, said outside the court: "It has been a long and anxious time for everyone involved and the officers concerned have been the subject of the most intensive scrutiny.

"Whilst it is now possible for those officers to return to normal duties and continue their careers, our thoughts go out to Mrs O'Brien and her family.

'Minimum force'

"We deeply regret the death of Mr O'Brien and the distress suffered by the family."

Mr O'Brien, 37, a market trader and married father of seven from east Dulwich, south London, died at Walworth Police Station after being arrested at a christening for being drunk and disorderly.

The three officers told the Old Bailey they followed procedures taught during training when arresting Mr O'Brien.

Mr Ilett said he had used "the absolute minimum of force" when arresting him.

He said that with the help of other officers, he held Mr O'Brien face down on the ground, his hands handcuffed behind his back, with a knee on his back.

Heart attack

Mr Ilett denied being asked to let the man up, or hearing Mr O'Brien say he could not breathe.

It was only after Mr O'Brien had been taken to the station that Mr Ilett noticed his face had turned blue and he was not breathing, he said - at which point he began mouth-to-mouth resuscitation while an ambulance was called.

The prosecution had alleged the three officers used too much force to hold down Mr O'Brien for more than five minutes, during which time he succumbed to postural asphyxia.

But a pathologist for the defence said Mr O'Brien had suffered a heart attack due to his size and enlarged heart.