David Davis' resignation means Dominic Raab will walk a tricky tightrope on Brexit

No pressure, then, Dominic Raab. It is a high stakes experience for any politician to take on their first role as a Secretary of State. There's the scrutiny, the responsibility, the chance to prove yourself and the risk you will prove insufficient to the job, not to mention the endless red boxes of papers—all in addition to your existing tasks as an MP.

The sense of constantly walking on a tightrope, with most of the audience willing you to fall, can be intensely wearing on anyone who reaches the Cabinet Table.

But for Raab the pressure is even more intense than normal: to take on this particular gig, at this particular time, from that particular predecessor is to mount an especially challenging high wire, with a nasty gale blowing to boot.

It's in the brutal nature of politics that no sooner had David Davis resigned but people immediately began to ponder who might succeed him running the Department for Exiting the European Union. The job itself is at the centre of the huge task dominating the nation's politics, the UK's escape from the European Union.

Or, rather, it is meant to be at the centre of Brexit. In practice, the department has been sidelined in recent months by the Prime Minister's growing reliance on Olly Robbins, the civil servant who has become a villain to many Tory MPs.

Her decision to look to her adviser and not to her Brexit Secretary played a major part in causing Davis to resign.

In the words of his resignation letter, “the Cabinet decision on Friday crystallised this problem”—her official proposals for the Government's Brexit end-goal confirmed his frustration that May was allowing Robbins to rub out what were meant to be the UK's negotiating red lines.

Had Davis continued in the post, the sidelining would have continued. He evidently felt that any protest or argument short of quitting would be ignored, so he did the only thing he could while honouring his principles.

That decision propels the department back into the limelight—at least temporarily reversing Downing Street's desire to pretend it does not exist.

But in short order Raab must face a variation on the same challenge which drove Davis to resign: how to maintain credibility among Leavers and loyalty to the Prime Minister's plan at the same time?

Credibility is important both personally and politically.

Personally, because a young, ambitious Eurosceptic like Raab will understandably have an eye on what his fellow Conservative Party members think of him—particularly given that there's a growing chance of a leadership election soon.

Politically, because if the Brexit Secretary is no longer lead negotiator then the primary responsibility of his role is to publicly demonstrate that the Government is staying true to its promises to deliver a proper Brexit.

That was Davis's function, and it is one reason why a fellow Leave supporter who was once his chief of staff has been appointed to succeed him.

The first Brexit Secretary found it impossible to square his Eurosceptic principles with the demand to be loyal to the Prime Minister's Chequers plan. The second Brexit Secretary will be focused right now on how he might possibly manage to do so.

His new job—the one he has worked so hard and risked so much to secure—is made all the more difficult by the fact that its previous occupant has effectively said he cannot be true to his beliefs and to the Prime Minister.

The fact that the Foreign Secretary has now concluded the same, and followed suit in resigning, only ups the pressure on a uniquely challenging first day in office.