I've never understood the issue of Jeremy breaking into the farm after he was bailed on 13th September. 
As a result of Mugford's statement Jeremy Bamber was arrested on 8 September 1985, as was the friend Mugford said he had implicated, though the latter had a solid alibi and was released. Jeremy told police Mugford was lying because he had jilted her.
Jeremy was bailed from the police station on 13 September 1985, after which he went on holiday to the south of France.
Before leaving England, he returned to the farmhouse, gaining entry by the downstairs bathroom window.
He said he did this because he had left his keys in London and needed some papers for the trip to France; he did not borrow keys from the housekeeper who lived nearby. When he returned to England on 29 September he was re-arrested and charged with the murders.
What other reason could he have had for revisiting the farmhouse so soon?