Men of the 'golden triangle' who pull the election strings

One is a royal courtier who enjoys shooting, another is the nation's top civil servant, the third works at Downing Street and likes listening to the Grateful Dead. When John Major finally calls the general election, this unlikely threesome will take up their places in the "golden triangle" of the British constitution.

Sir Robert Fellowes, Sir Robin Butler and Alex Allan will be the key people holding the fabric of the state together while the Government is in the three-week limbo of the election campaign,

Although the Prime Minister will tell the Queen when he wants to go to the country, it is his principal private secretary, Alex Allan, who will set in motion the end of Mr Major's current term in Number 10. The other points in the triangle will be top of his calling list. One is the Queen's private secretary, Sir Robert Fellowes; the other the Cabinet Secretary, Sir Robin Butler, the most senior mandarin in the country, whose career has spanned 36 years.

Sir Robert, the shooting enthusiast, is 56, served in the Scots Guards and joined the Palace in 1977. He is regarded as unassuming by the standards of royal courtiers. Mr Allan, a tall, curly-haired ex-Treasury official nine years his junior, has more eclectic interests: computers, sailing - and the Grateful Dead.

For the Prime Minister, who can choose the date of the election, the constitution is a flexible ally. Parliament must be dissolved (it does not have to be sitting at the time) by Royal Proclamation which is issued after a meeting of the Privy Council. The proclamation is given the Great Seal in the House of Lords, writs are issued for the new elections and nominations received in the constituencies.

Seventeen working days must elapse between proclamation and election, meaning that any Thursday between 17 April and 22 May is possible. It need not be a Thursday, although in practice it is almost certain to be, and an announcement within the next three weeks of a 1 May poll looks ever more likely.

One of Mr Major's first tasks is to call upon the Queen, and already Mr Allan and Sir Robert will have sized up all the possible opportunities. The obvious one is the regular weekly audience which usually takes place on Tuesdays at Buckingham Palace. This is a formal occasion with the Queen and the Prime Minister sitting opposite each other. The meetings are in the early evening and last for about an hour. Even if this is the cocktail hour, the beverage on offer is tea (nor does Her Majesty produce biscuits). Mr Major could then announce the election date with a statement outside Downing Street on Wednesday or Thursday, launching his manifesto shortly afterwards.

Alternatively the PM can request a separate audience on the day of the announcement as Margaret Thatcher did in May 1987. Every permutation will have been worked out and agreed by the golden triangle.

In reality the Queen's assent is a formality. She does not even need to be in the country and, indeed, was in the Caribbean in 1966 when Harold Wilson decided to go to the country.

Then a constitutional nightmare was narrowly averted by a relatively junior official checking the minimum number of working days between the proposed proclamation by the Queen and the election taking place. St Patrick's Day had to be discounted when it was found to be a public holiday. The dissolution would have to be brought forward. An emergency telegram was flashed to the Queen in the Caribbean. She signalled back her approval.

With the sort of symmetry only Whitehall seems to provide, the young official concerned was Robin Butler.

In all these events the golden triangle plays a supportive, mechanical sort of role. But if the result of the election is inconclusive - a hung parliament, the three become central players. Sir Robin and Sir Robert will together advise the Queen on when to ask a prospective prime minister to try to form a government.