Party politics has always been about factions – gangs of like-minded individuals getting together to promote a particular cause or point of view.
But Brexit has taken the natural tendency of MPs to plot and conspire with each other to a whole new level.
Like the rest of the country, the 2016 EU referendum divided MPs into two tribes – Leave and Remain.
For some MPs, these opposing visions of Britain’s future place in the world exert a far more powerful pull than party loyalty.
They sometimes find they have more in common with MPs in other parties who share their view on Brexit than those on their own side.
They rebel against their party leadership to vote for what they see as a bigger cause, even if the term “rebel” has ceased to have much meaning in the current chaotic climate.
MPs are described as rebels one day, for voting against their party leadership, only to become loyalists the next day and vice versa.
It will only get more intense when MPs return from their summer break and gear up for the “meaningful vote” they have been promised on any deal Theresa May strikes with the EU.
Some hope, or fear, that it could lead to a permanent reshaping of the political landscape as the big parties break apart and reform into new ones.
But for now, here is a guide to the main factions in the Commons:
Theresa May loyalists
Government ministers, basically – there are just over 100 them out of a total of 316 Tory MPs – and those backbenchers who support Theresa May’s Brexit policies, or at least are not willing to vote against them and threaten her leadership.
Most Tory MPs fall into this category but it is not enough for Mrs May to be sure of winning key Commons votes, even with the support of the DUP’s MPs, who unlike Mrs May backed Leave in the EU referendum.
Ten members of Mrs May’s government have quit in recent months – most of them because they are against her Chequers plan for post-Brexit trade, although Defence Minister Guto Bebb quit because he is in favour of it. Mr Bebb thought she had caved in to the hard Brexiteers (see below) over customs legislation.
Tory hard Brexiteers
Sixty Conservative MPs, headed by Jacob Rees-Mogg, are members of the European Research Group – a pro-Brexit lobby, who are against Theresa May’s plans for trading arrangements with the EU.
They are well-organised and highly motivated and the PM’s continued survival in Number 10 is, largely, in their hands.
The rebel ranks have been swollen by ex-Foreign Secretary Boris Johnson, former Brexit Secretary David Davis and his deputy Steve Baker.
Tory soft Brexiteers
The Dominic Grieve gang. Like most of his cohorts, who number about a dozen and include former minister Nicky Morgan (seated behind Mr Grieve in the picture above) who led an unsuccessful rebellion in the customs vote, the former attorney general is not a natural rebel.
Mr Grieve and his supporters inflicted the government’s first Brexit defeat, in December, securing a “meaningful vote” for MPs on the final deal with Brussels, but some wonder whether his gang have the killer instinct of their pro-Brexit rivals when that final showdown happens in the autumn. Mr Grieve has said he will quit the party if Boris Johnson becomes prime minister, in reaction to a row over the former foreign secretary’s comments about the burka.
Conservative MP Anna Soubry, a close ally of Labour’s Chuka Umunna in the People’s Vote campaign for another EU referendum (see below), has called in the past for the creation of a new centre-ground party.
She has also backed a call by fellow Conservative Sir Nicholas Soames – a longstanding pro-European and the grandson of Sir Winston Churchill – for a “government of national unity”, made up of senior figures from different parties to sort out Brexit.
Lib Dem leader Sir Vince Cable has long been calling for more cross-party co-operation to fight Brexit. He told BBC Radio 4’s Today programme “reasonable” people from all parties wanted to avoid the possibility of chaotic “no deal” Brexit.
“The conditions are there” for a change in the traditional line-up of parties, he added.
Tory second referendum group
Former Education Secretary Justine Greening is the most senior Conservative to have called for a referendum on the final Brexit deal. She was backed by Heidi Allen and Anna Soubry, and another prominent backbencher, Sarah Wollaston, has also joined the People’s Vote campaign.
Loyalty is highly prized by Labour leader Jeremy Corbyn – hardly surprising given the number of his own MPs who have tried to oust him – and many of the new intake of Labour MPs, as well as his inner circle, are fully behind his Brexit stance. His backing for Britain’s departure from the EU – after supporting Remain in the referendum – was seen as helping the party gain votes from Leave supporters at last year’s general election.
Some longer-serving Labour MPs, including former ministers from the Blair/Brown era, suspect he is a Eurosceptic at heart and are frustrated by his refusal to call for another referendum, even though he has shifted in a “softer” direction by calling for a customs union with the EU after Brexit.
People’s Vote group
About 30 Labour MPs who back a new EU referendum have, arguably, been operating as a party-within-a-party for some time under the People’s Vote and Open Britain banners.
Although a cross-party campaign, with the backing of the Lib Dems, Green MP Caroline Lucas and Tories Anna Soubry and Sarah Wollaston, People’s Vote is dominated by Labour figures in open revolt against their leadership’s policy of opposing another referendum.
Leading figures include Chuka Umunna, Chris Leslie and Stephen Doughty. They tend to drop their party label when commenting on Brexit, preferring to be described as People’s Vote supporters.
Like the members of the People’s Vote campaign, the SNP’s 35 MPs, led by Ian Blackford (pictured) are against Brexit and want the UK to stay in the EU single market and customs union.
They have said they won’t stand in the way of a second referendum but have not committed to voting for one. One reason for this is that Scotland voted for Remain in 2016 and it did not make any difference to the result.
They are likely to vote against anything resembling a “hard Brexit”.
Kate Hoey (pictured), John Mann, Frank Field and Graham Stringer – along with the currently independent Kelvin Hopkins – voted with the government in key Brexit votes, helping to ensure Theresa May’s survival.
This is the core of a group who say they are standing up for the millions of Labour supporters who voted to Leave the EU.
Shadow Chancellor John McDonnell has urged them to stop propping up Theresa May’s government. Ms Hoey is facing calls from her local party to be expelled from Labour, something she is “quite relaxed” about, and Mr Field’s constituency party recently passed a no-confidence vote in him.