Officers searched woods between Foxholes Lane and Lumsdale Road, in Matlock, last Thursday, but were unable to find clues which could help identify the man who robbed the 16-year-old.

The victim held little hope the criminal would be caught. He said he was still shocked and depressed following the robbery, but wanted to move on from it.

"I just want my coat back from the police now and to not have to think about it," he said.

"I'll carry on going on walks as I really enjoy it, but not on my own and perhaps not when it is dark either."

The innocent victim had been enjoying a stroll near Lumsdale quarry at dusk on Sunday January 24, when a man approached from behind and held a sharp object to his back.

The Highfields School pupil said: "I felt something sharp in my back, and a man saying 'I don't want to do this, man, just give me your phone'.

"I instantly froze and handed my mobile over my shoulder. It was nearly pitch black and was terrifying. I waited until I heard him move away, then scarpered."

The victim thought it was likely to have been an unplanned robbery, by a desperate person.

Sniffer dogs and officers had combed woods in the hours immediately after the attack, but there was some confusion about the exact site of the robbery and the search was fruitless.

Det Sgt Tim Nye, of Matlock police station, urged residents to call him on 0345 123 3333 if they had seen anything suspicious in the area near the time of the attack. He added: "I think people should take some care and maybe in the short term if they do go walking up there, go with someone else.

"This is a really isolated location and that's the unusual thing and from a fear factor point of view it ramps it up quite a bit."

The robber, thought to be in his early 20s, did not have a Derbyshire accent.