Work will involve repairs to failing beams in the citadel and shower room areas that support the cellblock structures.

Atkins senior group manager Gary Self said: “We look forward to addressing the unique challenges of this project, such as working on an island that is only accessible by boat, with no land lines for telephone or data services.

“Not to mention we’re facing the cold, strong, hazardous currents of the San Francisco Bay and the penitentiary’s chilling past.”