I'm not trying to defend this rogue in any way but you are back to accusing him of stealing although that is what it might appear. For instance if I gave my car keys to a friend who then refused to return the car it is a civil matter and the police would take no interest.
The theft act of 1968 has a couple of paragraphs which describe his actions:
A person who by any deception dishonestly obtains property belonging to another, with the intention of permanently depriving the other of it, shall on conviction on indictment be liable to imprisonment for a term not exceeding ten years.
Where an offence committed by a body corporate under section 15, 16 or 17 of this Act is proved to have been committed with the consent or connivance of any director, manager, secretary or other similar officer of the body corporate, or any person who was purporting to act in any such capacity, he as well as the body corporate shall be guilty of that offence, and shall be liable to be proceeded against and punished accordingly.
A corporate body would normally be a company, organisation or group of people, possibly the army are exempt. Either way it seems strange that a custodial sentence was not applied.