The police investigated Durham and concluded no law had been broken. It always was perfectly permissible to have a beer whilst working.
The police investigated the birthday event and concluded the law had been broken. It was never permissible to have a non-essential work gathering to eat birthday cake with the birthday boy's wife and interior decorator present, to say nothing of a photographer.
Do you understand the difference now, @JaniieJones? One broke the law, one didn't. To say nothing of the fact that the one who broke the law not only was responsible for making the law but lied about it repeatedly to Parliament. It really is quite a big difference, you shouldn't be struggling this hard to understand it.