Knights, 42, was released on temporary licence to go to an address in Newhaven, on March 22 East Sussex but failed to return by 4pm today.
As a result Knights has now been reported as missing to the police.
Knights is currently serving a five and a half year sentence for burglary.
He is described as being white, 5ft 9in tall, of medium build, with brown hair, and a tattoo of a British Bulldog on his right arm.
Anyone who may have seen Knights, or who has any information regarding his whereabouts, is asked to contact Suffolk police on 101.
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