Watson has been missing from the prison since October 8, when he failed to return from an authorised week-long release, while Craig didn’t come back from unsupervised release last Thursday.

Craig is less than a third of the way through a nine-year sentence for crimes including assault, and his case has led to fresh criticism of the assessment process at Castle Huntly.

The prison, part of the open estate with Noranside, in Angus, was the subject of a Government-ordered review after an inmate raped a schoolgirl while on the run.

Anyone with information about the whereabouts of Watson or Craig is asked to contact the police.