A long-term prisoner who taunted police while on the run has had an extra 16 months added to his sentence.

James Boyle was serving eight years in HMP Castle Huntly near Dundee when he went AWOL for a fortnight during a routine home visit on February 1, this year.

After failing to show up for a pick-up at Buchanan bus station in Glasgow on February 8 he initially claimed he had food poisoning but soon disappeared off police radar.

During the period he was missing, the 24-year-old from Clydebank, West Dunbartonshire, started posting pictures on social media site Instagram boasting about the drunken nights out he was enjoying with friends.

He was caught nearly a fortnight later when police found him staying in a friend's flat in Govan, Glasgow.

Boyle, who was jailed in 2012 for assault to severe injury, danger of life and attempted murder with a knife, had been let out of Castle Huntly prison for 13 previous home visits.

While he was on the run, Police Scotland issued a warning to the public not to approach Boyle because of the potential danger he posed.

When captured, he claimed he had been told his victim in the 2012 assault had been plotting a revenge attack at Buchanan bus station, saying he would have been a "sitting duck" if he had turned up.

At Perth Sheriff Court on Tuesday, he admitted going on the run after being allowed out of Castle Huntly for a week-long temporary home leave.

Solicitor Kenny Clark, defending, told the court that: "This was by no means a sophisticated or Machiavellian plot.

"He buried his head in the sand and spent time sofa surfing at friends' houses but was never more than ten miles from his family home in Clydebank."

Sheriff Gillian Wade said: "You had been released out on licence very many times and knew clearly what the rules were.

"It will be a matter of great disappointment to you that you will now spend a considerably greater period in custody."