YOU probably haven’t heard of Sir Christopher Geidt, the Queen’s private secretary. But you soon may. For in the bleary hours of the morning of May 8 – should the electoral calculus produce a hung parliament – Sir Chris will be at the heart of the process to cobble together a new government. He is one apex of the so-called “golden triangle”, together with Cabinet Secretary Jeremy Heywood and Chris Martin, the Prime Minister’s principal private secretary. Collectively, they will orchestrate negotiations with the palace that must end in Britain’s next Prime Minister being called to Buck House to kiss hands.

Geidt gets angry – not to mention litigious – at any suggestion he is anything other than an anonymous cipher, a mere liaison person between the monarch and her ministers, and someone with no opinion of his own as to who forms the next government. To suggest otherwise is to invite the accusation one has watched too many episodes of Wolf Hall. No, no: Sir Christopher is no Thomas Cromwell, no Establishment eminence grise!

However, read the private secretary’s job description on the official royal website and one finds this: “The Private Secretary informs and advises The Queen on constitutional, governmental and political matters in the United Kingdom and the Commonwealth.” In other words, should Britain find itself without a majority Government when the sun rises on May 8, it will be Geidt who “advises” the Head of State on the constitutional niceties of what happens next. Others will no doubt struggle to be heard but the “adviser” closest to the ear of the Queen is Geidt.

No-one could be more Establishment that Sir Christopher Geidt KCB, KCVO, OBE. He was born in 1961 and attended prep in Oxford before being sent to the pukka Glenalmond boarding school in Perthshire. In 2007, pupils at Glenalmond hit the headlines after they made a spoof video that featured them “hunting” local working-class “chavs” on horseback and shooting them with shotguns – it’s still on YouTube. In 2008, a BBC fly-on-the-wall documentary exposed a culture of bullying at Glenalmond. One pupil complained: “When I first came here I was called a chav because I had a strong Scottish accent.”

In point of fact, Geidt is Scots on his mother’s side – a Mackenzie. His grandfather, Kenneth Mackenzie, was a fish curer and coal merchant before setting up a successful Harris Tweed factory in Stornoway, where he later became provost. Geidt still owns a 365-acre sheep farm on the Isle of Lewis, and has been seen helping with the lambing. Whether he purred following the referendum result, I have no idea.

After Glenalmond, Geidt enlisted in the Scots Guards and was subsequently commissioned as an officer in army intelligence. By the way, Geidt hates being referred to as a spook. From 1994, he worked for the Foreign and Commonwealth Office and EU in sensitive diplomatic postings, such as Sarajevo at the height of the Serb-Bosnian war. He actually liaised directly with Radovan Karadzic and the odious General Ratko Mladic, both later indicted for war crimes.

In October 1989, Geidt and another former army officer turned up in Pol Pot’s Cambodia ostensibly to observe Vietnamese troops pull out of the country. During a subsequent House of Commons debate, Labour MP Bob Cryer used parliamentary privilege to query why Geidt was there: “Surely not MI6?” In 1991, Geidt sued the left-wing journalist John Pilger over a TV documentary that accused him of training Pol Pot’s Khmer Rouge. This accusation was clearly nonsense and Geidt won substantial damages. However, his career history is a curious mix of military intelligence, security analysis and crisis diplomacy. That hardly suggests his current role is a sinecure.

Geidt is routinely described as “suave” but he can also be prickly. In 2013, he complained to the Press Complaints Commission regarding critical articles in the ultra-liberal Guardian newspaper. He repudiated The Guardian’s claim that he personally was “one of the final arbiters” of a new and more restrictive Royal Charter on press regulation. The paper insisted there was a clear public interest case for investigating Geidt’s role in the Charter. However, the PCC upheld the complaint and the offending articles have been purged from the paper’s website. One up to the Establishment.

I dare say that Geidt genuinely believes he is a mere liaison chappie. Equally, I think he was recruited by the Royal Household to provide the monarchy with a worldly wise political adviser capable of protecting it from an intrusive media, and piloting it (with privileges intact) through the constitutional whirlwind unleashed by devolution. We have to bear that in mind come the election.

Geidt will reply that the cardinal rule of Britain’s archaic, unwritten constitution is that the monarch acts only on the advice of ministers. However, the whole point of having an unwritten constitution is that “precedent” can be junked the moment the Establishment finds itself in an existential crisis. The Crown is “kept out of politics” so it can be invoked as a referee when the Establishment’s interests are threatened, especially by a popular democratic upsurge. That is Sir Christopher Geidt’s real job.

We’ve been here before. After the inconclusive General Election in 2010, the SNP proposed to Labour the formation of a “progressive alliance” to keep the Tories from entering Downing Street. With the LibDems, SNP and smaller parties of the left, Labour could have commanded a working majority on major votes of between 23 and 31. Goodbye bedroom tax and NHS privatisation. Instead, Labour made ineffectual overtures to the LibDems alone. Sensing he had the upper hand, Nick Clegg demanded Gordon Brown quit as PM. Brown resigned office – but before a replacement government had be agreed. Convention requires the existing PM hold the fort until someone emerges who can command a parliamentary majority.

There was consternation at the palace in case the Queen found herself having to pick a PM quickly without political cover. Fortunately for the Establishment, Sir Christopher Geidt was on the case. According to Peter Riddell of the Institute for Government: “Geidt was very active. His role was a kind of super-journalist: to find out what is going on … to find out the political mood and developments, and report this back to the Queen.” Geidt was able to report that Cameron and Clegg wanted to tie the knot. The palace could safely twiddle its thumbs in anticipation.Crisis averted.

Current polls predict a reasonably healthy left-of-centre majority in the next House of Commons – provided there is a big bloc of SNP members. The danger lies in the British Establishment and the rabid London media working to divide any prospective progressive alliance before it gets started. If negotiations become protracted, we will hear talk of constitutional crisis and threats to the future of the Union. Cameron, as sitting PM, will try to cling to office. Subservient Labour backbenchers with an eye on a peerage will bleat about the need for national unity. There will be much talk of the need to keep the Queen “above the fray”. All in all, a situation tailor-made for the peculiar talents of Sir Christopher Geidt.