Last week saw the clearest exposition of the UK’s negotiating position on Brexit. Not from the prime minister, who had had a go the week before in Greenwich—nor from other possible candidates—Dominic Raab, the Foreign Secretary, Priti Patel, the Home Secretary, or indeed Michael Gove, the Chancellor of the Duchy of Lancaster, aka the minister in charge of most things the PM needs getting done.

Instead it came from a prime ministerial aide. Not the one most of the media is obsessed with, but arguably the one who will do the most to shape the UK’s future—the PM’s designated chief EU negotiator David Frost. But the fact that he was setting out the government’s approach—and his personal “journey” to Brexit—raises a host of interesting questions.

It is easiest to see David Frost as a straight line successor to Olly (now Sir Oliver for his pains) Robbins. Indeed he is objectively much better qualified for his role than Robbins ever was. Brussels experience—tick. European diplomatic posting—tick. Trade policy experience—tick. External industry representation—tick. If he had applied for the job within government, or to an external job advertisement, he would have been a strong contender with those credentials.

But that is not how he got the job. Frost is a special adviser, appointed by the prime minister. But he is a special adviser performing a task that goes, well, a long way beyond “advice.” No one would blink an eye if he was sitting in No 10 as the latest in a long line of foreign affairs or Europe advisers to the PM. But instead he seems to be taking a much more active role—an amalgam of the roles exercised before by the Brexit secretary—a cabinet minister—and a permanent secretary, Robbins.

If this is how the PM wants to run the negotiations, fine. Much better to have someone in charge he trusts. But he owes it to the rest of us to explain how this will work in practice and in particular how the accountability gap it leaves will be filled.

First, special advisers are supposed (at least formally) to keep their mouths shut. The special adviser code says they should “normally” steer clear of public utterances on controversial issues. the fact that no one has taken any action against Frost, indeed that his speech has been lauded, suggests that he has cover for the exception. But is he talking for himself? For the PM—who made his own pitch the week before? Or for the government—did any other minister have a chance to comment?

Second, Frost cannot answer questions from MPs or make statements on the floor of the House. Who do MPs get to quiz when they want to interrogate the latest UK negotiating position? Is PMQs the only option? Will Michael Gove pick this up at Cabinet Office questions?

Third, will Frost appear before select committees? The Exiting the EU Committee is in the process of being re-established despite the loss of the department it shadows. The Lords EU committee is up and running. Brexit secretaries had their run-ins with select committees over their hesitancy to appear—but ultimately they showed up, sometimes in to-be-treasured double acts with Robbins. If Frost does not show up, will scrutiny have to focus on the civil servants who work with him, or whoever is deemed to be his official boss (Mark Sedwill? Or the successor to Cabinet Office permanent secretary John Manzoni?) Or will parliament have to rely on the prime minister finally accepting an invitation from the Liaison Committee, which expects to grill leaders regularly but has so far been rebuffed?

And finally, has Frost been given authority over the civil servants who form his “Task Force Europe”? Special advisers are not supposed to manage civil servants, so how does that work?

None of these questions mean that Frost is the wrong person for the job. But they do suggest that Sedwill and the PM have some work to do to clarify how Frost’s role is intended to work in practice—and how it fits with the current adviser code. And if that code is no longer fit for purpose, they need to tell us and revise it.