If he has now spent it and is once again skint, then he can legally start to get benefit again. They can only count what you have now not what you once had. I know about deprivation of assets ,but he only has to say he was paying off money owed or helping relatives and friends.
Was there not a case a two or three years ago where someone won over £2 million on the lottery , blew the lot. Then successfully went back to claiming benefits? It was all over the news at the time.