Jeremy was a thief. Robbing the caravan park.
Mugford was the one who told the police about the caravan park.
The jury believed Mugford.
Yes, Jeremy was a thief when he stole from the caravan park, he was not involved in the cheque fraud carried out by Julie and her mate, that was quite a crime imo. Julie was taken by the police to the bank in order to confess and apologise, she sold her soul to save her skin and her career and banked £25, 000.
Not sure the jury believed her, or many others actually, it was the silencer that convicted Jeremy and we know how discredited that is now.