“Erst kommt die Fressen, dann kommt das moral” (roughly translated as: “Grub first, then we’ll talk about morality”) wrote that dreadful old Marxist cynic Bertolt Brecht in his Threepenny Opera, and his words rang in my head as I read Theresa May’s sour effusion in The Daily Mail berating Boris Johnson and Donald Trump for their lack of “moral values”.

When a politician – and a spectacular failure of a politician at that – starts to prate about morality then you really do need to start counting the spoons. May’s bitter little homily, though, is sadly typical of the parade of failed former prime ministers who, like decaying Draculas rising from their coffins, regularly return from the political graveyard to lecture us on our own various failings and that of their successors.

Most pathetic of them all is the grey man himself: John Major. Not a month goes by without this bitter and twisted old man creaking out of his retirement to raise his querulous voice yet again in a TV studio or lecture hall, croaking out a sermon on the folly of Brexit and the glories of his beloved European Union.

If May or Major’s time at the top had seen even a smidgen of success on any front perhaps that would entitle them to descend occasionally from their Olympian heights to correct our courses. Instead, both presided over years of shame, misery and bungling ineptitude that ended in disaster for them personally and defeat for the Tory party that they led so ingloriously into the mire.

Let us – however reluctantly – return to those records.

Major was the classic case of a man who rose without trace to hold the highest offices of state with no noticeable qualifications for doing so. Having arrived in Downing Street in the giant footsteps of the woman who had so unwisely promoted him, Margaret Thatcher, he proceeded to do his fumbling best to destroy her many achievements.

His treasured central policy of tying Britain to the ERM – the European Exchange Rate Mechanism, precursor of the Euro – ended in catastrophe on 16 September 1992, also known as Black Wednesday. Britain was forced into a humiliating withdrawal from the ERM at the cost of a cool £3.5 billion, leaving millions in mortgage misery and smiles on the faces of fat cat speculators who had profited from the debacle.

Tony Blair left half a million dead Iraqis in his wake as a permanent memorial to his premiership

That same year, Major had bludgeoned and arm twisted his reluctant party into voting for the Maastricht Treaty: a stepping stone towards sinking Britain into a federal European superstate and destroying her sovereignty as a free and independent nation. The culmination of his appalling reign was his ridiculous “back to basics” policy, supposedly returning morality to politics, which was inevitably followed by a string of sordid sex scandals featuring Tory MPs including Major’s own adultery.

The voters passed their own verdict on Major in 1997 with a landslide victory for Tony Blair’s New Labour, the biggest defeat for the Tories since 1945, which kept the party out of power until 2010. After such an unbroken record of political failure an honourable man might have been expected to retire beneath the nearest rock, never to be seen or heard from again.

But this is to underestimate the overweening vanity and sense of entitlement of former prime ministers.

Those qualities, coupled with personal vindictiveness and lack of self-awareness, are shared to the full by Mrs May who, difficult though it is to believe, equalled or even outperformed Major’s record of unredeemed failure in high office. Her sustained but utterly unsuccessful attempt to overturn the 2016 referendum result and keep Britain under the control of the EU is too recent to need reiterating, and it might be kinder to draw a veil over such unhappy memories were it not that May herself insists on reminding us of them.

But both of these monumental walking disasters are trumped in shamelessness by Tony Blair. For all their staggering incompetence, neither Major nor May – nor  did the much-reviled Donald Trump – leave half a million dead Iraqis in their wake as a permanent memorial to their premiership. That ignoble record belongs to Blair alone.

But that doesn’t stop the junior partner in George Bush’s illegal war from popping up on our TV screens to offer his views and advice on everything from stopping Brexit to dealing with the coronavirus pandemic. He is now even apparently entertaining fantasies of emulating General De Gaulle in returning from the wilderness to some form of power.

The last thing we need from this tragic trio is advice about how to get it right when they got it so disastrously wrong

The horrible habit of these rejected and reviled ex-PMs in offering their unwanted counsel and criticism of their successors began in the 1970s with the original “incredible sulk” Edward Heath. Another disastrous failure during his thankfully brief period in office, Heath had the impudence and vanity to attack his successor Thatcher – a greater and more successful PM than he in every respect – not that that would have been hard to achieve. Incidentally, it may or may not be coincidence that all four of these failed PMs were great fans of the EU.

It would be a huge relief to the nation if Major, Blair and May realised that there is nothing so ex as an ex-PM and firmly buttoned their loose lips. The last thing we need from this tragic trio is advice about how to get it right when they got it so disastrously wrong. In the immortal words of Clement Attlee – a better PM than the three of them put together – to Harold Laski, a carping Labour colleague who had constantly criticised him: “A period of silence on your behalf would be welcome.” Hopefully a permanent period.