When a relationship turns sour, there's a familiar phrase employed in the aftermath: once the trust had gone, there was nothing left. So what are we supposed to do when the bond of trust between we the citizens and the instruments of state is broken? Go for some counselling?

The incident – if indeed that's what it was – which took place last September involving the then Chief Whip Andrew Mitchell and the policemen on duty in Downing Street was, on the face of it, pretty small beer. A politician with a notoriously superior bearing was asked to get off his bike by a policeman who was being fastidious (perhaps to a fault) in applying the rules.

In his irritability, Mr Mitchell swore at said copper. This much, as far as I can tell, is not disputed, and in a different, less highly-charged, time, that might have been the end of it.

However, oaths are one thing, classist insults are another. He called me a pleb, said the policeman. I most certainly didn't, countered Mr Mitchell. And because we don't trust the political classes any more, because we think they've all got their noses in the trough, or even the duck house, we were all too willing to accept the word of the bobbies on that particular beat. The newspapers were, the public were, and David Cameron was. So Mr Mitchell was booted out of office on the back of what now looks like a confected charge.

So where does that leave us now? We lost faith in those who run our banks some time ago, the expenses scandal did for politicians, and we have just spent more than a year inspecting every piece of our national newspapers' dirty linen. Are there no institutions we can rely on any more? Well, only the good old BBC... oh, hold on a minute.

But this is on a different scale: if you can no longer trust the police, where does that leave us as a society? Which is the question I'd like to pose today. I said at the time that this whole affair had a fishy smell about it, and it does now appear that Mr Mitchell was tucked up like a kipper.

So, on the same day that the Home Secretary announced that there is to be a major investigation into police actions during and after the Hillsborough disaster, we are told that there is to be an inquiry into what happened the evening Andrew Mitchell allegedly went tonto in Whitehall. And who's going to be investigating the actions of members of the Metropolitan Police? Why, the Metropolitan Police of course.

I heard the MP Keith Vaz on the radio yesterday morning demanding a more independent inquiry. But as I listened to Mr Vaz's perfectly reasonable argument, all I could think was: weren't you involved in the Hinduja affair, and didn't you once claim £173,000 in expenses in a year?

Everywhere we look, we are finding it harder and harder to trust those who are meant to govern us, protect us, and look after our interests. We need help, because without trust, all we have is suspicion.