Lying in a drawer in a bedroom in Wales is a gold pocket watch - a testament to an act of bravery that happened 77 years ago in Camden.

Charles Thomas Williams, better known as William Williams, was a conductor on the buses when he spotted two policemen being attacked in Camden Town.

Without a thought for his own safety, he jumped off the bus and waded in to their aid – and ended up in St George’s Hospital, in Tooting, south London, with concussion, where he stayed for two to three weeks.

In recognition of his valour, Mr Williams was awarded a gold fob watch from the Metropolitan Police

Now, years later, Mr Williams’ family is desperate to unearth the details of the incident.

But the only thing known about the event is the inscription on the timepiece, which reads: “Presented to William Williams esquire by the officers of Kentish Town Station, N Division, Metropolitan Police, in appreciation of his courage in going to the assistance of two of their officers who were being seriously assaulted in Camden Town on 10 June, 1935.”

Mr Williams’ only son Peter, 72, who lives in the former coal-mining Welsh town of Abertillery, where his father was born, said: “He never spoke about it. He just used to say, ‘It was one of those things. You would have done the same, son’. He was as reticent as anything.

“In those days, Irish troubles were abroad and there was a huge Irish contingent in that area, so maybe it was connected with that. But the police say they have no record.”

Mr William was born in 1901 and worked in the colliery from the age of 14 to 18, when his strong singing voice saw him win a scholarship to the Guildhall in London. After completing his studies, he stayed in London – living in Mercers Road, Tufnell Park – where he worked on the buses while also singing for an opera company.

But in 1941, he was called up to serve in the Second World War, enlisting in the RAF, and his wife Elizabeth returned to Abertillery to have their son.

After the war, Mr Williams also returned to his home town, getting a job with British Nylon Spinners and working there until his retirement.

Mr Williams died in 1982 at the age of 80, leaving behind his wife – who died six years later, his son and two grandchildren. He now also has two great-grandchildren.

“I have his watch,” said Peter. “I don’t wear it but my dad used to use it regularly. I can see him now, pulling it out of his pocket.”

* If you can help trace the details of the incident in 1935, contact the Ham&High newsdesk on 020 7433 6215 or email editorial@hamhigh.co.uk.