The dramatic and yet inevitable withdrawal of Rupert Murdoch's bid for BSkyB serves as a vivid symbol of giddy decline, a collapse from swaggering omnipotence to breathless fragility in less than a fortnight. Suddenly there is a mountain of inquiries and investigations into the activities of the media, the police and politicians. Until recently only a few were bravely and passionately interested in the implications of News International and the hacking allegations. Now one media empire is besieged and others must be wondering whether they too will attract unwelcome attention.

Perhaps more staggering revelations are to come, but the essential contours of the scandal are clear. Power in Britain is distributed widely and erratically. Yet on the whole we report and scrutinise decisions, events and public personalities on the assumption that most power is concentrated in the hands of politicians in general and ministers in particular. Around the clock, politicians are held to account, even though most of them wield virtually no power at all. If anything happens anywhere, the instinct of the media and the gladiatorial parliamentary culture is to hold the Government to account almost alone. Weak-kneed elected politicians feel compelled to respond.

This dynamic reached a neurotically extreme point during Tony Blair's premiership when he felt obliged to issue a statement expressing concern about a fictional character in Coronation Street. Whatever is wrong with our political system, politicians are kept on their toes, accountable to the media, parliamentary committees and, of course, the electorate that can kick them out.

This form of robust accountability is largely healthy. To reverse the proposition and argue that elected figures should not be held to account would be deranged. But the consequence of an excessive focus on mainly insecure, scared politicians has led to a distorting lack of accountability in relation to non-elected institutions that wield power with anonymous, and often unjustified, self-confidence. Few voters had heard of the senior bankers who were leading them to the edge of the precipice until it was almost too late. And yet the likes of Sir Fred Goodwin, who steered Royal Bank of Scotland towards catastrophe, had far more power than most elected ministers who were regularly attacked on the front pages and summoned to explain their timid, powerless behaviour at 8.10 am on the Today programme.

Similarly, only now is more intense scrutiny being applied to the activities of the Metropolitan Police and the quality of some of its senior staff. The accountability of the police is highly sensitive and complex, but some senior figures in the Metropolitan Police have sheltered under convoluted lines of scrutiny. Both the Mayor of London and the Home Office have theoretical powers, while police retain operational independence. In fairness, the head of the Metropolitan Police is a public figure and extensively scrutinised, but it was alarming to watch the Home Affairs Committee interview a former assistant commissioner, Andy Hayman, and a current holder of that rank, John Yates. How did such cocky mediocrities rise to senior posts, ones that gave them responsibilities for handling the threat of terrorism? No elected minister would get so far up the Cabinet in the way that unimpressive duo rose up the hierarchy of the police. The media and parliamentary scrutiny would have exposed their different flaws long ago. Yates wields more power than most ministers, and Hayman used to.

Some media organisations, but most specifically Rupert Murdoch's, have become the most extreme example of this trend towards unaccountable power. Murdoch rarely gives interviews. We have not heard from Rebekah Brooks since the latest revelations. According to the police officers interviewed by the Home Affairs Select Committee, News International failed to co-operate with their original inquiry, an inadequate excuse for giving up the investigation, but nonetheless the most damning of allegations. Here was a company that evidently thought it was powerful enough to get away with it, able to block police inquiries and to pay off victims of crime.

One of the most revealing episodes in this damning sequence relates to the recent payment by News International to victims of hacking, including Gordon Taylor from the Professional Footballers' Association and the actress Sienna Miller. The payouts were public knowledge and yet few did very much in response. In some respects this tolerance was more shocking than the appalling revelations about Milly Dowler's phone. It took an emotionally charged trigger to challenge the might of an empire that owns around 40 per cent of newspapers and until yesterday afternoon sought to become an even bigger broadcaster. Until the terrible twist in relation to Milly Dowler, no senior frontbencher dared to make a move, and it took immense courage from the Labour MPs Tom Watson and Chris Bryant to lead their previously lonely campaign.

A non-elected, largely unaccountable company acted loftily, while relatively obscure ministers with much less power are sometimes forced to resign for minor misdemeanours or no misdemeanour at all, quite often at the screaming insistence of newspapers owned by News International.

Cameron was in authoritative form in the Commons yesterday afternoon, conveying a sense of grip, even if no one is, in reality, gripping very much at all. It is a mistake to view this crisis through the prism of the immediate political fortunes of Cameron or Ed Miliband. While it is true that Miliband read the scale of the saga with astute perception and acted on it with flair, I doubt if voters view the fast-moving events in terms of the party leaders, but more with an exasperated, impotent horror.

The longer-term political prize is much bigger than one determined by which leader performs well in response to each volcanic eruption. I do not have great hope that the inquiry announced yesterday will deliver the prize. Its remit is wide and unavoidably abstract. To take one example of the difficulties when we move from the vague to the particular, Cameron stated yesterday that he supported "independent" regulation of the newspapers rather than self-regulation. When asked to explain the difference, he could not do so. I have spoken at many meetings where the relationship between the media and politics is the theme. The meetings go around in circles and always promise more than they deliver. This may be the fate of the inquiry.

But deeper currents move fast. Belatedly, a strange sort of enforced accountability is taking place as parliament reasserts its right to stand up to non-elected institutions that function in the dark. Some commentators suggest that this is a sinister development, possibly leading to excessive political interference. Such fears are unfounded. How can it be sinister when those we elect challenge lawbreaking by a non-elected organisation? There is instead the prospect of a healthy re-balancing brought about partly by some brilliant and persistent investigative journalism.

The many investigations will bring a form of catharsis, but the practical remedies are available for application now. If the media or the police break the law, they should not be allowed to get away with the crimes. Ownership must be limited, so that no single organisation holds excessive sway. The media and other institutions must scrutinise more robustly those in power beyond Whitehall or Parliament. We need to know a lot more about the activities of bankers, powerful business leaders, senior civil servants, police and, of course, what is happening behind the closed doors of media empires. This is a story about who runs Britain, and as light is shone we discover horrors. The light must not fade again.

s.richards@independent.co.uk;