The small matter of the monarch's cash should not obscure a bigger question

If Britain insists on retaining its monarchy, and there are some good reasons for it to do so, the Crown must undergo a minor revolution.

This weekend marks the culmination of the jubilee celebrations. Although it has been a difficult year for the Queen personally, it has been a highly successful one professionally; "The Firm" has shored up its support across the nation with a PR campaign that must make the so-called experts in Downing Street rather envious.

At such a moment, it is worth pausing to contemplate the future of the monarchy. This is a time of great constitutional upheaval, with devolution being extended, hereditary peers on the brink of exclusion from Parliament and the reshaping of Europe on the horizon. As our investigation into royal finances shows, the traditional British muddle cannot go on; we should debate, then decide, precisely the role we want our head of state to play.

There is little enthusiasm for the republican cause at present, although resentment and unease lies buried lightly beneath the surface in many influential quarters. However, it is our belief that the monarchy should undergo some fairly radical reform.

The Queen's announcement that she will rule until her death means the Crown cannot simply stumble on until the succession permits reform. This is a period of rapid change – in Britain, in Europe, in the world – but the monarchy remains essentially an Edwardian institution. The death of the Queen Mother has removed a formidable obstacle to modernisation. A shrewd monarch – and the Queen has shown herself shrewd – would take advantage of this period of warmth during the jubilee to re-establish the British Crown on a firmer foundation.

This resurgence of royalism will be transient. There remains immense respect, and even some affection, for the Queen. But the paraphernalia of court, the expensive trappings of her family and the activities of unpopular relatives look increasingly out of place. To take one example: does a modern monarchy need five places in London, never mind Windsor, Sandringham and Balmoral?

What the monarchy now needs to do – as much for its own benefit as for ours – is to re-establish itself as a useful, efficient institution that carries out its duties in a low-key manner and, in return, has the right to some privacy. A public family will always be of interest to the public, particularly if it behaves with the self-indulgence of this one. But a modest professional institution can claim the right to some curtained windows.

The ambiguities are all too chaotically contained in the present state of royal finances. Just what the precise nature of its difficulties are we cannot know. The Crown, in an antiquated throwback to its mediaeval origins, is above the fiscal scrutiny of its subjects (who, of course, pay many of the bills). Its assets, its shares and its private spending are all a closely guarded secret – even, amazingly, from the Keeper of the Privy Purse. The Queen oversees huge assets in land, property, art treasures, gifts and jewellery. But whether these strictly belong to the monarch as an individual or the state is ill-defined.

What is known is that, as a result of a combination of restricted income from the civil list, the falling value of shares and income from tourism and rising tax, her outgoings may exceed her income. Without a drastic cut in expenditure or a sale of assets she will have to return to the Commons to ask for more money within the near future.

Recovery from foot-and-mouth, a revival in the stock market and a reduction in the number of people receiving grants, grace-and-favour accommodation and flunkies could help. But it will not solve the basic tension between a family that continues to behave as if its was in the 1920s while living in the 21st century. There needs to be a new deal in which most of the Queen's palaces and art collections and many of her properties are settled in the hands of the state where they can be enjoyed by all. The state's contribution to the running cost of the Queen's public office can be settled anew and her children set free to earn their own livings. Ideally, the more immature sections of society would leave them to do so without hysterical outbursts over their successes and failures.

If Britain insists on retaining its monarchy, and there are some good reasons for it to do so, the Crown must undergo a minor revolution. It must adopt a more modest approach and become a monarchy that reflects far more accurately the lifestyles of its people. As with so many other parts of our national fabric, the pattern has been set elsewhere in Europe. Only if this happens will Britons continue to desire that their Royal Family should long reign over them.