A man on his way home from a Hallowe’en party was beaten to death by a group of thugs after he confronted one of them who had snatched his girlfriend’s witch’s hat.

Ben Gardner, 30, suffered fatal head injuries when he was punched and kicked to the ground in the attack in Sutton, South London, at 3.30am.

He and Allanna Devine, 28, had stopped for a takeaway at a kebab shop opposite Sutton Police Station.They passed a group of drunken men and women, one of whom snatched Ms Devine’s black pointed hat, which she had hired from a fancy-dress shop.

When Mr Gardner went after him and demanded it back, the thief is reported to have spat inside it before handing it over.

At that point other members of the group attacked Mr Gardner. His girlfriend was also punched, and left with minor injuries.

Mr Gardner, a spreadsheet developer for Legal & General, was taken to St Helier Hospital. He never regained consciousness and died of his injuries on Sunday evening.

His friend Will Fearnley-Whittingstall, a cousin of the television chef Hugh Fearnley-Whittingstall, said that Mr Gardner was “never the sort to get in any trouble, but he would put his life on the line to defend those he cared for”.

Mr Gardner grew up in Sutton and was brought up by his grandmother after his mother died. He played darts for a local team and supported Liverpool Football Club.

Six weeks earlier he had served as the best man at Mr Fearnley-Whittingstall’s wedding.

Mr Fearnley-Whittingstall told The Times: “Above all, he was a normal guy. He had just recently bought a flat, he had got a new flat and a new girlfriend.”

Another relative, who did not wish to be named, said: “He adored his grandmother and she adored him. She’s absolutely in bits.”

Ms Devine was too upset to speak to reporters at her home yesterday.

Five men in their early 20s and two women aged 25 and 26 were being questioned at several South London police stations yesterday. They remained in custody last night. One man who was arrested shortly after the attack in the early hours of Sunday has been released and will face no further action.

Detective Inspector Bob Campany, who is leading the investigation, said: “This appears to be a violent unprovoked attack on an innocent man who was out enjoying Hallowe’en night with his girlfriend.

“Although it was 3.30am, there were a lot of people in the area at the time of the incident as the local clubs were closing. We would like any information from witnesses who may have been on Throwley Way at the time.”

A former girlfriend of Mr Gardner’s, writing on the website of a local newspaper, described him as “a lovely guy who did not deserve this”, and expressed her dismay that the attack was not interrupted by the police. “Sutton is usually crawling with police at night,” she wrote.

Part of the street in central Sutton was sealed off as part of the investigation. Metropolitan Police statistics show that the South London borough has an average overall crime rate, but a lower than average rate of serious violent crimes in the capital. There were 12 in the borough in September.

Some residents blamed the area’s burgeoning nightclub culture for recent incidents. “At one time Sutton was known as one of the safest boroughs,” a local taxi driver said. “Whereas years ago most young lads went to Kingston and caused trouble, it’s the other way round now.”

The British Crime Survey, released last week, indicated that half of all violent attacks on men in 2008-09 were inflicted by strangers.

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