It seems that during the break-in Mountain saw something in the shed that caught his eye.
According to the prosecutor Dominic Howells: ""He told officers he was coming down off amphetamine and felt overwhelming need for sexual relief."
The bear in question didn't attempt to fight off his advances, but if it had it would have looked something like this.
The trouble for Mountain was that as a result of this tryst, he'd left his DNA at the crime scene.
This post originally stated Darwen was in Lincolnshire rather than Lancashire. This was almost certainly because the author hadn't had his coffee at the time of writing.