Two men have admitted conspiring with a convicted murderer to spring him from custody during a hospital visit in what was an "entirely naive" plan foiled by police.

Officers covertly set up audio and video surveillance when they discovered the plot to help Robert Paterson escape from custody, and intercepted.

John Wilson, 29, Scott McAllister, 39, and Paterson, 32, admitted conspiring, between January 12 and January 17, to defeat the ends of justice and help Paterson escape from lawful custody while he was on a pre-arranged visit to Wishaw General Hospital.

Paterson was a prisoner in HMP Shotts at the time.

The trio pleaded guilty when they appeared before Lord Bracadale at the High Court in Glasgow.

Wilson and McAllister admitted visiting the hospital grounds to establish a way for Paterson to escape in a vehicle and, on January 17, left a car there with the ignition keys and a mobile phone inside.

Paterson was convicted of murder in 2008 and sentenced to life imprisonment.

Defence Advocate Ronald Watson QC, representing Paterson, said his client was ordered to spend a minimum of 20 years behind bars.

"Therein perhaps lies the reason for any plan that was devised. Mr Paterson is a relatively young man. He has been in custody all these years and anticipates spending many more years in custody," he said.

Describing the escape plan as "entirely naive", Mr Watson said: "There was no plan to effect his escape or even a suggestion of how he was going to escape the hospital.

"There was no suggested plan as to how he was to evade recapture or escape the jurisdiction."

Ann Ogg, representing Wilson, said her client "sincerely regrets" his involvement and that there was no suggestion of any violence in the plan.

McAllister's lawyer said that his client felt under pressure to be involved.

Christopher Stewart, 29, was originally charged with being involved in the conspiracy but his not guilty plea was accepted by the crown.

He admitted supplying diazepam, a controlled drug, between January 11 and 17 at a flat in Castlemilk, Glasgow.

The men were due to be sentenced at the High Court in Glasgow today.