Who is David Davis?

The long-serving Conservative MP was among the new intake when Tony Blair’s new Labour swept to power in 1997. In the two decades since, the former SAS reservist has become an established figure within the party, challenging David Cameron to a 2005 leadership contest which the younger man went on to win. He would become a key ally in Theresa May’s embattled Cabinet.

Why was he important to Theresa May?

The no-nonsense politician revelled in the description of being Britain’s “Brexit bulldog”, charged with leading negotiations with his EU counterpart over the country’s withdrawal from the bloc. He has been noted by former colleagues for his “tough, resilient” approach. His role as Brexit Secretary was crucial to ensuring Britain leaves the EU next year with what Mrs May described as the “best possible deal”.

So what does this mean for the PM?

It’s hard to imagine a more potentially crippling blow to her premiership. Following a long weekend which started with extended talks over the country’s future relationship with the EU at Mrs May’s Chequers country pad, an agreed strategy met the backing of her Cabinet. It seemed like the most damaging line to emerge from the summit was Foreign Secretary Boris Johnson’s description of the plans as a “turd”. But as the weekend grew older, dissenting voices from the Tory backbenches grew louder. In short, the PM is facing the prospect of steering the country towards the biggest political junction in a generation without her captain at the helm.

BrexitAttentions will turn to how David Davis’s departure will affect Brexit negotiations (PA)

Was Davis’s departure telegraphed?

The Brexit Secretary was understood to have serious reservations about both the plan and whether it could be acceptable to Brussels following the Chequers summit, but was absent from the television studios in the aftermath of the talks. He has been close to the exit door on a number of occasions in recent months. Last year reports emerged that Davis said he intended to “retire” in 2019 and leave the transitional period of Britain’s exit from the European Union to Boris Johnson, something later dismissed as a “lighthearted remark”.

Is Davis the first of many?

There was a feeling that any departure – be it immediately after the summit or once the EU made it clear Britain’s terms were unacceptable – could trigger a series of resignations from the front benches, particularly from hardliners. Mrs May must be expecting others to go with Davis, and will be particularly keen to know what the likes of Mr Johnson and fellow Brexiteer Andrea Leadsom intend to do now.

Could it get any worse for the PM?

Yes. An avalanche of departures would surely trigger a leadership contest in the Tory party. Simply, if the Prime Minister cannot unite her Cabinet and convince them over the Brexit negotiations, she has no chance of getting the EU to agree to the terms.