An armed robber, who claimed cash he was caught with after a knife raid was "prison benefit money", has been jailed for eight years.

Robert Williamson stole the money from a newsagent's in Glasgow just weeks after being released early from an 11-year prison term.

The High Court in Edinburgh heard how the 30-year-old demanded cash from an employee and pointed a large knife towards her before threatening to tie her up and put her in a cupboard.

After taking £166 from the till he left and police were contacted. His description was circulated and officers stopped him nearby.

Williamson was found to have £169 in notes and pound coins on him. He claimed never to have been to the shop and told officers the cash was "prison benefit money".

A knife was found in undergrowth close to where he was detained with his DNA on the handle. He was also picked out at an identification parade.

Williamson, of Hillpark Drive, Glasgow, admitted assaulting Lorraine Montgomery, robbing her of money and illegally possessing a knife.

The court heard Ms Montgomery, 57, was working in the shop in Clarkston on August 31 last year when Williamson came in and said: "Give me the money."

She took it to be a joke but then realised he was holding a large kitchen knife, which he pointed towards her. The robber took cash from the till and threatened to tie her up before running from the shop.

Williamson had been released from a previous jail sentence, imposed for robberies and assault, on August 11 last year.

A judge told him: "You re-offended in a serious manner only a matter of a few weeks after being released on licence from sentences imposed for analogous conduct."

Lord Turnbull ordered Williamson should serve two years of the unexpired part of his previous sentence followed by a further six years for his latest crime. The judge also decided he should be under supervision for a further four years.

Defence counsel Michael Meehan said he had emphasised to Williamson the need to take part in courses in prison if he was "to break the cycle of re-offending".