But the police have nothing to prove his guilt.

It is not a police matter. No crime is alleged.
The police are considering taking action against the ex-cops.

Jim,
Then it doesn't concern you that the discovery of porn on the computer wasn't investigated at the time, which is an indication that it existed?

There is no evidence that it existed, apart from the allegations ten years later. If it did exist it was not a police matter because there was no criminal activity and it would have had no bearing on the investigation.

People seem to be overlooking this accusation by a Tory activist

It is currently being investigated. There is no cover up.