Michael Brown: Pity the Queen with a new PM

By polling day, she could have endured four prime ministers since the last election (three unelected)

"The Queen will decide who will become the next prime minister and leader of the Conservative Party". Those are the words of the BBC account of the developments on 9 January 1957, following the resignation of Sir Anthony Eden as Prime Minister. Fifty-one years later, as she heads for her summer holiday in Balmoral, it looks as though Buckingham Palace may need to pack, in her picnic hamper, detailed advice on choosing the next Labour prime minister. For although the Queen has been through this process on 11 occasions, she might be going through it on two more occasions this year in complicated circumstances.

Of course, in the days of Queen Victoria, the Prime Minister would have been on hand throughout the summer Balmoral holiday to give a constant update on any crisis. Gladstone details at length a typical day spent at Balmoral – on 31 August 1863 – "walked 24-and-three-quarter miles today – found it too much for my stiffening limbs". But he considered that "this place is, on the whole, very beautiful and satisfactory". He was still there on 7 October – with even a routine Cabinet summoned north of the border.

Of course, the present Queen will have barely 36 hours in the company of the Prime Minister at Balmoral in a few weeks' time. But it will be the Eden resignation that preys on her mind as she barbecues Mr and Mrs Brown's sausages while Labour's woes continue.

A year ago this week, I recorded on this page how Sir Anthony, having become Prime Minister in 1955 in similar circumstances to Gordon Brown, sought a dissolution of Parliament – within six seeks of his appointment and was returned after the general election with an increased majority. But having failed to emulate Sir Anthony's only political success – or to take my advice – Mr Brown now appears to be struggling to last in office as long as Sir Anthony. It will require another 236 days as the tenant of Number 10 before he is safely past this dubious milestone.

The circumstances surrounding Sir Anthony's resignation should remind the Labour Party to spare a thought for our dear Sovereign. Should any one of three scenarios – the Cabinet greybeards, the cumbersome processes of the Labour conference in Manchester next month, or a petition of 70 Labour MPs requesting a contest – materialise, Mr Brown will presumably tender his resignation as Labour leader while a two-month party contest to find a successor ensues.

But does he resign immediately as Prime Minister? If he were to have, by implication, lost the confidence of his Cabinet and his MPs in the Commons, it would seem impossible for him to continue to appear at PM's questions, chairing the Cabinet and generally going about his prime ministerial business during the two-month leadership hiatus. He would surely resign at once.

So the talk would then turn to the question of an "acting prime minister". Except that there is no such thing. Acting party leaders? Yes. But the Queen's government must continue and Mr Brown's last audience with the Queen would require him to advise Her Majesty on whom to summon as the 53rd prime minister. One can imagine the conversation: "Ma'am, most of my senior colleagues are squabbling for my job – including the deputy party leader Harriet Harman whom I might otherwise have recommended if she were not a candidate. But if I recommend any of those standing in the Labour leadership election – Miliband, Straw, Denham, Johnson – I will be accused of showing favouritism, although my blessing may actually also be seen as the kiss of death."

Perhaps the Queen's response might be: "What about that chap who came to see me about the Budget – Darling? He's not standing is he – I know you made him Foreign Secretary recently and, after all, you do say it's only for a couple of months. Would he do?" After Sir Anthony's resignation, when the Tory Party still allowed its leaders to "emerge", the Queen decided she needed additional advice on whether to summon Rab Butler or Harold Macmillan. She turned to her own greybeard, Sir Winston Churchill. One wonders whether on this occasion she might ask one or all of her three surviving ex-prime ministers – Thatcher, Major and Blair – to step round to offer advice.

So assume Mr Darling trots round to the Palace to "kiss hands" with the Queen as she responds "you're my 12th prime minister". Quite what she would make, after handing him the seals of office, on being told that he will be back in a couple of months to return them, can only be imagined. Alistair Cooke, the revered custodian of the Conservative Party's own modern history, posed to me an alternative suggestion, following newspaper reports that Margaret Beckett might be brought back into the Cabinet. She served as acting leader of the Labour Party following the death of John Smith. After her surprise appointment in 2006 as Foreign Secretary, Mr Cooke is betting on yet another Margaret becoming prime minister.

I may now be in the realms of fantasy, but imagine some unexpected grisly event, occurring during this period, enabling the temporary prime minister to shine in the manner of Vince Cable – with calls for the appointment to be permanent. Suppose Labour MPs rally to this unexpected success while the eventual winner of the leadership election gets support from the constituency parties and trade union sections while failing to get a majority of Labour MPs. More problems for the palace.

But whoever wins the party contest would surely have to give a public commitment to hold an early general election. Thatcher, Major and Blair provided 28 years of the Queen's government. By polling day, she could have endured four prime ministers since the last election (three unelected) before she gets round to counting Mr Cameron in – and eventually out.