Sometime between 17:30 on Friday 16 April and 08:00 the following morning, offensive language and imagery was drawn on a bench, walls, worktops and glass of a greenhouse.
Police believe the offenders had gained entry to the Castle – which was closed at the time – via scaffolding.
Anyone with information or who witnessed the offenders is asked to contact PC95 Jefferies on 222 222 or to contact CrimeStoppers anonymously on 0800 555 111.
Pictured: The scaffolding around Castle Cornet.