Cometh the hour, cometh the man. With Theresa May otherwise tied up reading a lesson on the importance of nations remaining united – “whom the gods would destroy, they first make mad” – at a service to celebrate Commonwealth Day at Westminster Abbey, the government was in urgent need of someone to explain why no one in government had the faintest idea of what was going on.

The obvious candidate was the Brexit secretary. But Steve Barclay was automatically disqualified as he is too dim to realise quite how little he knows and therefore might unwittingly end up telling the truth. Asked a binary question, there is always a 50-50 chance of Barclay letting slip the wrong answer. But in junior Brexit minister, Robin Walker, Downing Street had the perfect fall guy. A man with the ideal level of stupidity. Someone just bright enough to have an inkling of how out of his depth he really is.

What makes Walker even more ideal is that he is totally at ease with his limitations. Indeed, he embraces them. A minister who has never sought – nor indeed been offered – promotion. Being clever enough to know nothing has been the main reason why he is the only minister to remain in the Brexit department since it was created two and a half years ago. Far from being a hindrance, Walker makes a virtue of unfailingly polite ignorance. In all his outings at the dispatch box, he has never knowingly said anything that could possibly be construed as helpful.

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Jeremy Corbyn was only moderately grumpy that the prime minister hadn’t shown up in person. After all, it wasn’t as if her answers would have been any more enlightening. Not least because there was no one in the entire country with any answers. May was merely the inadequate busker-in-chief. So having everyone’s time wasted by Walker was only really an act of lèse-majesté against the British state. And on the scale of the government’s current crimes against the country, that barely rated as a misdemeanour.

Mumble, mumble, mumble. Walker kept his eyes down, staring lovingly at his red ministerial folder, thrilled to find his brief had been reduced to repeating what everyone already knew from listening to the news. The Brexit negotiations were still going on and something may or may not happen as a result. If anyone ever did find out something definite, then they would first tell the prime minister, who at some point might get round to telling the European Research Group and then parliament. But whatever did happen, he was entirely confident he would be the last to hear about it.

The Labour leader tried to press Walker on details. What changes to the backstop were the government seeking? When would the attorney general deliver his verdict? Would the meaningful vote take place on Tuesday? And would the prime minister again vote against her own deal by accepting an amendment the EU hadn’t agreed?

Walker merely smiled and looked a bit blank. All this was so far above his pay grade, he couldn’t possibly comment. Especially with the possibility of a Chilcot-style inquiry into the government’s mishandling of Brexit in the offing at some point down the line. So all he could do was repeat what he had already said. Something may or may not be happening but whatever the result it was his job to know absolutely nothing about it whatsoever. The plausible deniability of the truly ignorant.

Some on the Labour benches, such as Hilary Benn and Yvette Cooper, did make a desperate, futile plea for some clarity, but with Walker method-acting the part of his department’s latest idiot unsavant, the Commons quickly degenerated into an echo chamber as MPs read whatever they wanted into his answers. An exercise in which Walker was delighted to be complicit.

Owen Paterson and Nicky Morgan, who has now morphed into a fully paid-up Brexiter, both declared themselves delighted that the minister had implied the government was actively pursuing the Malthouse compromise with a taskforce of badgers armed with stun grenades and a barcode scanner. Night vision goggles as added insurance.

Tories Julian Lewis and Maria Caulfield said they were reassured that Walker’s silence meant that if the EU were to offer the UK a last-minute deal, then it was a clear sign that the EU had always been an untrustworthy bunch of bastards. Typical bloody Johnny Foreigner. Making the PM fly to Strasbourg with a possible way out of total humiliation.

This was too much even for Walker. His replies became ever more terse and clipped, as though he hadn’t quite banked on there being MPs even more out of touch with reality than him. At this rate, they might even get his job. He spelled it out once more. No one had a clue. And anyone who said they did was lying. If the government was on the board of a plc, then it would be sued for corporate negligence.