A JEWELLER, who left South Africa to escape violence and crime, was threatened with a knife and a screwdriver when he tackled thieves who stole a £12,500 diamond ring from his shop.

Tim Platten, owner of The Jewellery Workshop, High Street, Old Amersham, pinned down one of the thief's accomplices after he bolted from the shop.

But the South African had to let him go when the thief returned with the weapons.

He said: "We moved from South Africa to get away from this sort of incident, but now this has happened."

A young man, aged about 18 to 19, came into Mr Platten's shop on January 26 and asked to see the 18-carat gold ring.

Mr Platten, 33, was showing him the ring when another man was let into the shop. The first man grabbed the ring and made off with it in a waiting red Metro driven by another accomplice.

The 6ft 2in South African was helped by a passer-by who held down the second man while the police were called. But moments later the getaway car returned and the first man leapt out armed with the knife and the screwdriver.

The offenders are described as white, and about 5ft 6in to 5ft 8in tall.

Anyone with information should call police on (01494) 465888