An age-old mystery has been solved after an amateur historian finally discovered why a rugged rock face in the Lake District is known as Policeman Crag.

Raymond Greenhow researched public records and papers to discover that the crag at Clough Head, near Threlkeld, was named after Pc James Armstrong, who died in the line of duty after losing his way in the darkness and falling to his death.

Locals had always referred to the spot as Policeman Crag, but the reason why had been lost since the officer’s death, more than 150 years ago.

Mr Greenhow, who works for Cumbria Police, identified Policeman Crag to be Pc Armstrong after seeing a reference to the death of a policeman in a report of an inquest held at the Royal Hotel in Keswick on October 4 1847.

The report said that the week before, Pc Armstrong set out to travel from Keswick to Pooley Bridge on foot to execute a warrant of a non-payment of a fine.

Following the payment, Pc Armstrong made his way back to Keswick but became lost in the darkness and, instead of keeping to the road, his disorientated route had taken him high up Wanthwaite Crags.

He fell more than 300ft to his death.

The 40-year-old left behind a widow and three children.

He has now been added to the Cumbria force’s roll of honour, for officers who have died in the line of duty.

Mr Greenhow said: “The incident has lived on in the memory of the local people of Wanthwaite and Threlkeld, with the specific crag now referred to as Policeman Crag in memory of a pillar and protector of the community.

“His death shows the demands on a police officer back then, with the execution of a warrant taking days to complete in what would have been difficult weather conditions.”