Politicians have always had a reputation for backstabbing, but recently Westminster has been a battleground of back, front and side-stabbing in all parties. The shadow cabinet trying to oust Jeremy Corbyn after the EU referendum; Michael Gove abandoning Boris Johnson to make his own Tory leadership bid; and now Johnson himself derailing Theresa May’s set-piece Brexit speech with his Telegraph essay on the subject – and rumours of a resignation threat.

On the surface, it seems Brexit has given politicians licence to flout cabinet collective responsibility – the convention that binds our ministers to showing a united front on government policy.

The doctrine of cabinet collective responsibility was outlined in the Ministerial Code in the early Nineties, but it became a convention in the late 19th century “the way in which we talk about it still today, in terms of people failing to adhere to it”, says the Institute for Government’s Dr Cath Haddon, an expert in the constitutional issues of Whitehall.

It even goes back earlier than that, when the cabinet would have to bond in the face of a more powerful monarch.

But are we witnessing the end of this convention? It looks like we could be living in a new age of disloyalty. After all, the shadow cabinet was allowed to say what it liked about its leader over nearly two years, and Johnson is still in a job.

An unfaithful history

“I think it’s nothing new,” says Michael Cockerell, who has been making political documentaries and profiles for the BBC since the Seventies. “If you think back in time to Julius Caesar and all the rest of it, this loyalty to the leader is not something that automatically happens or has been normal both in history and modern democracies – there have always been rebels, always been ambitious figures who all work out exactly how far they can go.”

He says the situation with Johnson reminds him of Tony Benn, who was an outspoken cabinet member under Harold Wilson and Jim Callaghan in 1974-79. “He knew exactly how far he could push it without being sacked, because of the old thing about having him inside the tent pissing out, rather than outside the tent, pissing in.”

Cockerell believes that Johnson, like past cabinet rebels, knows “how far” he can go in defying May because she’s in a precarious position.

“Often if a prime minister is weak, that’s when the ambitious members of the cabinet can parade their disloyalty while still claiming they’re being loyal,” he says. “Most people who are disloyal always profess their loyalty.”

The peer and former Lib Dem leader Ming Campbell, who has been in politics since the early Seventies, also believes “it’s always been like this” in terms of disloyalty.

He gives Wilson’s governments as a past example. “There was a fair amount of disloyalty within the cabinet,” he says. “I remember it being suggested by someone that the cabinet meetings were often very, very quiet because people were so busy writing down things that they could put into print sometime later.”

“Fast-forward to John Major and the ‘bastards’,” he says, recalling the former Conservative prime minister’s battle with trouble-making Eurosceptic cabinet members in 1993.

Dr Haddon adds the examples of Margaret Thatcher being brought down by her cabinet (and tackling the “wets and dries” in her early years as PM), and Tony Blair and Gordon Brown’s teams briefing against each other.

She believes “nothing changes” regarding disloyalty because of the way British government works. “The UK system really provokes this sort of situation,” she says of Johnson. “Because we have empowered secretaries of state, we have a sort of federalist structure, and then we have the prime minister in the position of primus inter pares [first among equals].”

The idea of the prime minister being a fully empowered leader in control of a team is a “modern concept”, according to Dr Haddon. “If you go back into the nineteenth century, ministers were very much heads of their own little fiefdoms. We’ve always had this system that has enabled ministers to effectively have their own take, their own position in their particular roles, and able to speak publicly on their perspective.”

She says the same happens in the shadow cabinet because of the nature of opposition in the UK. Shadow ministers don’t receive tailored funding for their work, and are therefore “often very much reliant upon their own team” to develop policy proposals, “so they become quite autonomous”.

How disloyalty has changed

However, disloyalty plays out differently in modern politics. Campbell points out that with politics developing in real time online and through 24-hour news, there is a far greater journalistic focus on disloyalty. “Previously it would’ve been in the Sunday papers, now you get it 24 hours a day, seven days a week,” he says.

Dr Haddon believes pronouncements of disloyalty are more “overt” than they were because of the way we communicate on social media. Platforms like Twitter discourage the “coded messages” of past disloyal ministers, and show infighting more starkly.

“There is this immediacy of reaction,” she says. “And that it’s constrained to 140 characters leads people to ever more brief, succinct declarations of their position. We are also living through a period in which, dare I say, hyperbole and strength of position are only exaggerated by that medium. There’s something in that which is very different.”

And even though British political history is littered with attempted coups, betrayals and outspoken ministers – particularly over Europe – there is a sense that the rulebook has been thrown out recently, perhaps as Brexit has defied the status quo.

Collective responsibility and the idea of the prime minister as primus inter pares are conventions, and conventions can be moulded or dropped completely.

“The constitution is open for discussion now to an extent that I can’t remember,” says Campbell. “You’ve got arguments about independence, constitutional arguments which arise out of Brexit, if we leave. In those circumstances, it’s perhaps not surprising that the constitutional convention about cabinet responsibility comes under strain as well.

“If you’ve got a constitution that depends upon the observance of convention, then of course it’s much easier to depart from these if you choose,” he adds. “And in the present, febrile atmosphere of constitutional change, maybe it’s hardly surprising that what is thought to be a centrepiece is simply being disregarded.”