Prison escaper Kevin Polwart has admitted robbing a security guard of $60,000 while on the run from police last month.

Polwart, aged 40, appeared yesterday in the Porirua District Court and pleaded guilty to the new charge, as well as escaping from prison and the unlawful possession of weapons.

He will appear in the Wellington District Court for sentencing on August 17.

Polwart cut through a Rimutaka Prison fence with wire cutters about 6.30 am on June 7, police told the court.

The next day, in Palmerston North, he hired a locker at a self-storage company, where he put a Mossberg shotgun, 190 rounds of 9mm ammunition and 26 shotgun rounds.

At 1.50 pm on July 6 he went to the Three Kings Plaza in Auckland, armed with a pump-action shotgun and wearing a black balaclava. He approached an Armourguard security officer leaving the Foodtown supermarket with the day's takings.

The guard ran for the van when he saw Polwart, but Polwart cut him off and threatened him with the gun.

Polwart told the officer to open a locked compartment in the van and give him more money. More than $40,000 in cash and $19,500 in cheques was taken.

The van driver handed over the keys at gunpoint and Polwart left in a grey sedan driven by an unknown associate.

On July 17, police surrounded a Porirua house where Polwart was staying. He tried to escape but got only a short distance.

Police said Polwart acknowledged his part in the robbery and told them he had bought a van with $1500 from the proceeds.

He told police he had no choice but to escape from jail because of pressure they had placed on him.

Polwart said he needed the firearms, because the media had in effect put a $250,000 price tag on his head after his jailing for the aggravated robbery of an Armourguard van in Paraparaumu in 1999.

Polwart was serving a 10-year sentence for the 1999 robbery, which netted nearly $600,000. A large amount of the money has never been recovered.

Police are continuing to investigate the Auckland robbery.