Police state?

It seems to us the question that needs asking over the bugging farrago is this: why did the Metropolitan Police feel the need to listen in on conversations between Sadiq Khan and his constituent Babar Ahmad? Could it have had anything to do with the Met's concerns that Khan wanted to bring legal action against the police? The money para in the Guardian's coverage is this:

Police bugged a conversation between Khan and Ahmad as the pair discussed a civil action the inmate was bringing against the commissioner of the Metropolitan police, Sir Ian Blair, for an alleged assault by Scotland Yard officers, it was claimed yesterday.

The Grauniad doesn't make clear who is making those allegations, but if they're true, shouldn't we be asking questions about whether Blair was involved in the bugging decision? And why hasn't he said anything yet?