Some 35 years ago the first volume of Spike Milligan’s war memoirs — Adolf Hitler: My Part in His Downfall — were published. His wartime experiences were clearly an inspiration for what was to become The Goon Show.

For instance, when he was asked by an officer who found him lurking in an “inappropriate” place “Milligan? What are you standing there for?”, he replies: “Everybody's got to be standing somewhere, sir.”

It can be on this logic alone that Boris Johnson is standing for Mayor of London. Politics has closed down for the summer in every sphere except for the race to be the Conservative champion in the capital city. The term “race” is, however, rather an overstatement. Four candidates have been selected by the Conservative Party to woo the activists and then members — plus anyone else who wishes to participate in the process. They are Mr Johnson, Mr Neverheardofhim, Ms Neverheardofher and Mr Neverheardofhimeither.

This is less an election than an assumption. It resembles a presidential ballot in an African country that is in reality a dictatorship but where the incumbent has decided to demonstrate his democratic credentials by permitting a couple of random goat-herders and the odd elder from a very small tribe indeed to be pitted against him. David Cameron has similarly designed this battle so that Boris will face Ken Livingstone next May. I can see why this might (just) make sense for Mr Cameron. But even at this very late stage Boris should realise that it will do nothing but harm to him.

I consider myself to be uniquely placed to offer this counsel. For if I were to publish an account of my early adult life I could call it Boris Johnson: My Part in His Rise.

My role was, admittedly, somewhat accidental. It springs from the fact that I was the campaign manager for Boris’s opponent in the only electoral struggle of consequence that he has lost, when he first stood to be the President of the Oxford Union Society in 1984. This debating society had traditionally been dominated by a small cadre of students educated at a tiny number of elite schools — such as Eton College, from which Boris hailed — but it had by then fallen on hard times and was reduced to the indignity of having to encourage oiks who had come up from the state sector to become members.

The old guard believed, nevertheless, that they remained entitled to control the place. The young Boris was visually quite striking, as he has stayed, but not remotely as appealing. He hung around with the likes of the now Earl of Spencer (who did not court the company of those who had attended comprehensives) and was every inch the stereotypical Old Etonian, Balliol College (and High Tory) establishment contender to be president.

His rival was Neil Sherlock (a big cheese in the accountancy profession today, how the mighty have fallen) and I therefore ran a campaign of unremitting class warfare against him. If I threw a political punch that landed above the belt, then it was entirely unintentional. Poor Boris did not have a clue what had hit him (other than that it hurt) and was destroyed. He licked his wounds and a year later stood again for the same office. During that time he completely reinvented himself. He was interesting and funny. He implied that he was a supporter of the SDP (which, like Duran Duran, was trendy at the time) and was emphatically not part of the old ruling order. He was thus unstoppable.

He will be eminently stoppable if he takes on Mr Livingstone. There are three reasons why he should look forward to the encounter with fear and foreboding.

The first is that he will not be able to be the Boris he has become. The public and the pundits will demand that he proves that he is “serious”, and this will be the death of him. The ideal means of removing Red Ken from power is to make the election into a referendum on him and him alone. That cannot happen if Boris is the Conservative alternative. Ken will hit him harder than I did in his student days and will turn the election into a referendum on whether “this clown should be put in charge of the 2012 Olympics”. The mayor's distinctly undistinguished record will become immaterial.

Secondly, Boris is incapable of maintaining discipline until next spring. A disaster of some form is inevitable. He will either be exposed as having, how shall I put it delicately, “leafleted” several female London radio newscasters, or something he once wrote insisting that citizens who travel on a London bus are hopeless losers will be unearthed. Or maybe he will turn up in Hackney and declare what fun it is to be in Henley. Perhaps all of these mishaps will occur simultaneously. The media, an industry where (unlike Papua New Guinea) cannibalism is rife, will skewer him mercilessly.

Finally, it could easily be the end of his political career if only because of timing. The most plausible date for a general election is not this October/November but next May on exactly the same date as the London mayoral event. If so, then in late March Boris would have to decide whether to stand down from his parliamentary constituency to show that he is solely focused on his bid to depose Ken, or run again in Oxfordshire and rip his credibility to shreds by indicating that he did not think he would win in London. He will ultimately either drop out of politics altogether or stay in but be humiliated.

He should choose to avoid that Catch 22 situation. The Milligan memoir includes an account of an incident where a chef at his barracks attempted to disguise that he was keeping a pig (destined for Christmas dinner), which was against military regulations, by painting it brown and trying (but failing) to pass it off as a large dog. Boris is being painted brown by the Conservative Party at the moment. He should make a bolt for freedom.

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