THE design for a key that allowed a convicted killer to escape from a Territory prison was printed on the cover of a booklet given to all inmates, it has been revealed.

A former prison officer said the design of the master key - which could open every lock in Berrimah jail in Darwin - was printed on the front of the prisoners' information handbook.

He said a copy of the book was given to all inmates on arrival at the prison.

Daniel Heiss escaped from Berrimah jail in 1995, sparking a 12-day manhunt around Darwin.

His girlfriend Carolyn Wilkinson has just published his biography - Blood On The Wire.

In the book she claims Heiss escaped by memorising the detail of the key after studying it hanging from a prison officer's belt.

But the former prison officer who spoke to the NT News said authorities made the task much easier for Heiss.

"When I read that I thought 'What a load of bullshit', - it was much, much easier than that," he said.

"The prisoners' information handbook had a pair of crossed keys on the front of it.

"Those keys were a dead-set copy of the keys that we had. The key he copied was in the shape of a figure E, which was the master key."

The officer said it was Heiss's fellow inmate - fellow murderer Shane Baker - who made the key. He said Baker was a jeweller who had jewellery-making equipment in his cell, and used this to work on the key.

"Heiss was in a cell where he could reach his arm through the window and reach the lock," the prison officer said. "(Baker) was in a cell where he couldn't reach the lock.

"He used to give the key to Heiss and he would put it in the lock, then give it back and say 'I think it needs a bit more off here or there'."

Baker eventually designed a key that fitted the lock. Heiss let himself out of his cell before opening Baker's cell door. They got out of the complex by scaling three razor-wire perimeter fences.

Baker was recaptured within a few days but Heiss was on the run for 12 days.

The prison officer said Heiss left a message on his cell wall which read "This bird has flown".

The officer said Heiss's escape caused a huge amount of embarrassment for the authorities.

"The handbooks were taken off the prisoners straightaway and the contractors were called in to change all the locks," he said.