When Charles I arrived in the chamber of the House of Commons in January 1642, armed guards in tow, to arrest a group of MPs for treason, it was the speaker who stood in his way. Instead of giving up the so-called traitors, speaker William Lenthall rebuked the King and reasserted the power of the Commons, telling Charles, “I have neither eyes to see nor tongue to speak in this place but as this House is pleased to direct me.”

The struggle for power between executive and legislature is not a new one. But the possibility of John Bercow taking the lead in the battle to stop Brexit offers the prospect of a modern-day stand-off, every bit as compelling as the one that took place in the months before the Civil War. It’s not Jeremy Corbyn, Yvette Cooper or Ken Clarke who’s best-placed to stop Brexit, but Bercow himself.

It’s an opportunity that Bercow plans to exploit to the full. The reaction from Bercow today to Boris Johnson’s plan to hold a Queen’s Speech in mid-October, with parliament not sitting for a period of almost five weeks beforehand, was telling. He took time out from his holiday with his family to fire off a vicious message, saying that the PM’s plan is a “constitutional outrage” and an “offence against the democratic process”.

There was no need for this, of course. With a different person in the chair, you could expect the speaker to stay above the fray in such matters. Just as the Queen hasn’t knocked out a quick press release from Balmoral giving her two cents, so previous speakers would have kept quiet. Even if they did stick their oar in, other speakers might have given a more rounded view of where this planned prorogation sits in parliamentary precedent. Bercow could have pointed out that there is always a recess during September and October for party conferences; that the Queen’s Speech is long overdue; and that the PM’s plan will lead to the loss of just a handful of sitting days.

There was, however, no chance of any such approach. Bercow is someone who has always loved being the centre of attention. As his biographer, I should know. For him, supporting a cause means being the loudest voice in the room. When he was a Eurosceptic, Bercow was so fervent in his beliefs that he even vowed to carry on using French francs on his holidays, in protest at the introduction of the euro. Now he’s decided that Brexit needs to be stopped, his personality drives him, inexorably, to take up the fight more fiercely than anyone else.

Tariffs in the event of a no-deal Brexit Show all 15 1 /15 Tariffs in the event of a no-deal Brexit Tariffs in the event of a no-deal Brexit Pork There will be tariffs on pork in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Cheese There will be tariffs in place on some cheeses including €22.10/100kg of cheddar, €19.10/100kg of processed cheese and €18.60/100kg on some blue cheeses Getty Tariffs in the event of a no-deal Brexit Milk There will be no tariffs in place on milk Getty Tariffs in the event of a no-deal Brexit Car Parts There will be no tariffs on car parts imported from Europe PA Tariffs in the event of a no-deal Brexit Cars However finished cars will face tariffs of 10.6% Getty Tariffs in the event of a no-deal Brexit Alcoholic drinks There will be no tariffs on alcoholic drinks - except on some rums due to ingredients used in their distilling process Getty Tariffs in the event of a no-deal Brexit Beef There will be tariffs on beef in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Fish There will be no tariffs on many types of fish including cod, haddock, salmon and sea bass Getty Tariffs in the event of a no-deal Brexit Fruit and vegetables There will be no tariffs on almost all fruit and vegetables Getty Tariffs in the event of a no-deal Brexit Chocolate There will be no tariffs on chocolate or other cocoa products Getty Tariffs in the event of a no-deal Brexit Poultry There will be tariffs on poultry in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Ceramics There will be some tariffs in place on ceramis Getty Tariffs in the event of a no-deal Brexit Steel There will be no tariffs on steel Getty Tariffs in the event of a no-deal Brexit Coal There will be no tariffs on coal Getty Tariffs in the event of a no-deal Brexit Lamb/Mutton There will be tariffs on the meat of sheep in order to protect British farmers Getty

Nor is there much that the government can do to stop him. As speaker, Bercow alone can decide what’s permitted by parliamentary precedent, and he’s shown himself willing to ignore precedent entirely and to tear up the rules when needed.

It’s also easily forgotten that Bercow’s speakership is in the end of days. In the chair since 2009, he’s already outlasted a promise to stand down after two parliaments, and was almost toppled by a bullying scandal last year. In a future general election, the Conservatives are likely to use this as an excuse to run a candidate against him in his Buckingham constituency: Bercow would almost certainly lose. He may have just weeks left in the job, and he’s in need of a legacy.

So now will be the time for Bercow to push the nuclear button. I’m sure he will bend parliamentary procedure – or rip it up, depending on your viewpoint – to allow MPs to pass legislation requiring Johnson to seek an extension to Article 50, using a beefed-up version of the Standing Order 24 procedure, allowing for emergency debates. If there’s a prospect of revoking Article 50 before 31 October, Bercow will ensure that there is time for such a law to pass.

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But today’s events bring a more compelling prospect still. When parliament takes its five-week break – assuming MPs don’t block this first – Bercow will relish the idea of leading a parliament in exile. He can play his final hand as speaker: opening up the doors of the Commons in the face of the prorogation, running his own chamber as an act of defiance against the government.

In doing so, we would face a constitutional crisis like no other seen in modern times, with a direct stand-off between the elected government on one side, and the speaker, standing for some (but by no means all), of the House of Commons on the other.

A speaker hell-bent on stopping Brexit, with little left to lose, will be a very dangerous opponent for Johnson. Only one of their political careers can survive this confrontation. The outcome of this battle may well determine whether the government will survive – and whether Brexit will happen at all.