A convicted killer was able to escape from jail using the master key — which a fellow inmate had recreated from the cover image on a booklet handed out to all prisoners.

Daniel Luther Heiss was found guilty of murdering another man at a remote Australian cattle station and sentenced to life behind bars.

According to a new biography by his girlfriend Carolyn Wilkinson, Heiss memorised the shape of the key after seeing it on a prison officer's belt at Berrimah jail in Darwin. But a former guard has told Australian media an information handbook was the real source of details for the copy.

The image on the booklet was "a dead-set copy of the keys that we had," he claimed, according to News.com.au.

He added: "The key he copied was in the shape of a figure E, which was the master key."

Another inmate with jewellery-making equipment is said to have crafted the key. The guard added: "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'."

Even after letting themselves out, the pair had still to climb over three sets of razor-wire perimeter fence. Heiss was on the run for 12 days during the 1995 escape bid.