The Great Heathrow Mace Protest took us by surprise. We watched, goggle-eyed, as John McDonnell marched down the aisle that separates the Labour benches, a walking exclamation mark of outrage over his Government's decision to build a third runway at Heathrow. But when he reached the green carpet at the bar of the House, he looked, for just a moment, a bit lost.

He picked up the Mace. He did not grab it but lifted it gingerly, as if his real purpose might be to dust under it. For a few long tantalising seconds, the elaborate golden object rested on his palms, held out almost as an offering.

It looked wrong. Surely Mr McDonnell should be waving the thing about, brandishing it as Michael Heseltine had in 1976. That was a Tarzan moment. This, however, was a Mowgli moment.

MPs catcalled while Sir Alan Haselhurst, the Deputy Speaker, barked “Order!” Now Mr McDonnell, a rebel without a pause button, for he was stuck with it now, turned and carefully placed the Mace on the first Labour bench in a spot occupied until minutes before by Dennis Skinner, the Beast of Bolsover, who will be furious to have missed it.

“We represent the country,” shouted Mr McDonnell.

“Order!” snapped Sir Alan.

“We represent...”

“The honorable member must withdraw,” said Sir Alan, glacially cool, his words freezing in the air.

Mr McDonnell, his microphone fading: “This is a disgrace against democracy in this country!”

To his left, Geoff Hoon, the Transport Secretary, quit smirking. Mr McDonnell stood there – Mace at his side but, we must assume, at the ready. I looked on in disbelief, not at what he had done but that he had done it at all. The 57-year-old MP for Hayes and Harlington (which includes bits of Heathrow) is a serial rebel and an old lefty but he suffers from never being as interesting as he should be. But now, well, now, just this once, the grey man really was the star of his own Technicolor movie.

At this point, I did not think it was staged. Only moments had elapsed since Mr McDonnell had risen to rail against the decision. “It is a betrayal of my constituents who will lose their homes, their schools, their cemeteries...”

Something in his voice made me sit up and stare. Was that a catch? Was he going to cry? “It's a betrayal of this House and democracy not to have a vote IN THIS HOUSE.”

The paper in his hand shook: “Will there be a vote and why not?”

Geoff “Buff” Hoon, who failed to sense anything untoward (not for the first time), said there would not. Mr Hoon patted Mr McDonnell on the head as he praised him for fighting for his constituents and said: “But this is an issue for the country . . .”

Mr McDonnell shouted from his seat: “THIS IS THE COUNTRY!”

Mr Hoon, drone of drones, ploughed on: “Heathrow is a national airport serving the whole of the country and necessarily...”

Mr McDonnell began to walk. “THIS IS THE COUNTRY!” he shouted as he made his way to his date with the Mace.

In the end he was thrown out, suspended for five days. A few minutes later, outside Parliament on College Green, I chanced upon Mr McDonnell, standing by himself, no doubt awaiting a TV camera. Had he planned it? He allowed that it had been one of his options. Well, I wondered, why didn't you brandish the Mace? “I didn't want to damage it,” he said, I hope, sheepishly. He was, already, turning grey before my eyes.

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