edam a friend of mine who was not Met but worked with them closely told me most police officers were fair to middling, a good proportion were simply fantastic and a minority (not, sadly, a tiny minority) were absolutely dreadful: out for themselves, thuggish, dishonest, on a power trip and usually racist. Most don't come from London.
The problem as he saw it was that the system was not at all good at weeding them out and the fair to middling colleagues in particular tended to be afraid of the bad ones. They either went along with the cover-ups or put their heads down and stayed silent.
Also, the very good naturally get promoted quickly into specialist groups and senior ranks, leaving a disproportionate number of shits in the rank and file.
I've no experience of the police so can't judge.