In November, we argued that the Liaison Committee has a potentially critical role in helping deliver effective select committee Brexit scrutiny, and thereby also in Parliament’s overall Brexit performance.

We identified five Brexit-related tasks the Liaison Committee could usefully fulfil.

Four are largely behind-the-scenes: steering select committees’ inquiry choices to avoid duplication; perhaps going further into some light-touch strategic planning; ensuring committees are sufficiently resourced for Brexit; and engaging with the government on committees’ behalf on Brexit process issues (although this last could also generate some public questioning).

The fifth task, the questioning of the Prime Minister, is the most high-profile. Along with Prime Minister’s Questions, Liaison Committee evidence sessions with the premier are among the few parliamentary proceedings to appear routinely on mainstream TV news broadcasts. As such, the Liaison Committee’s performance could affect public perceptions of Parliament’s Brexit role.

Conducted effectively, Liaison Committee evidence sessions with the Prime Minister can also generate an important element of the historical record. And, compared with statement or question sessions on the Floor of the House, or media interviews, they offer an unparalleled opportunity to probe the premier’s thinking and decision-making, and hold her to account.

The current evidence session will be an important first test of the capacity of the new Liaison Committee - under new chair Dr Sarah Wollaston - to fulfil these roles, above all in relation to Brexit.

Vast amounts of Brexitry have taken place since the previous Committee last heard from Mrs May a year ago.

At that stage, the government’s Brexit policy consisted primarily of Mrs May’s 2 October speech to the Conservative Party conference, and her commitment to launch the formal Brexit process - by triggering Article 50 of the Treaty on European Union - by the end of March 2017. The government was still fighting the court case brought by Gina Miller and others on the need for parliamentary authorisation to invoke Article 50; and, in her evidence session, the Prime Minister was unable to commit to a parliamentary vote on any UK-EU Withdrawal Agreement.

Since last December, the Prime Minister and her government have, in order: delivered a major Brexit speech at Lancaster House, confirming that the UK would leave the Single Market and announcing a parliamentary vote on any Withdrawal Agreement; published a Brexit White Paper; secured Parliament’s authorisation to trigger Article 50 in the EU (Notification of Withdrawal) Act 2017, and done so; announced plans in the Queen’s Speech for seven further Brexit bills; introduced the EU (Withdrawal) Bill; delivered another major speech in Florence; announced plans for a Withdrawal Agreement and Implementation Bill to implement a UK-EU Withdrawal Agreement; and secured – after a delay in October and apparent DUP-related stumble in early December – the EU’s agreement on 15 December that ‘sufficient progress’ has been made in the opening phase of the Brexit negotiations.

That EU decision, opening the way to phase two negotiations from January on the terms for a post-Brexit transition, and from March on a framework for the post-transition UK-EU relationship, forms the immediate backdrop to the current Liaison Committee session.

But so does the government’s first parliamentary defeat since the general election, on 13 December on Amendment 7 to the EU (Withdrawal) Bill. As passed, the amendment requires Parliament to have approved any UK-EU Withdrawal Agreement in primary legislation before ministers may use the delegated powers in the EU (Withdrawal) Bill to implement it.

It will add piquancy to the current evidence session that Dr Wollaston was among the eleven Conservative MPs who voted against the government and for Amendment 7.

The Liaison Committee will question the Prime Minister as debate continues on the EU (Withdrawal) Bill’s final Committee Stage day, with a further contentious vote – on ‘exit day’ – due later in the evening.

The Liaison Committee session also comes the day after the Cabinet held what has been reported as its first formal discussion of the desired end-state for the UK’s post-transition economic relationship with the EU.

The Liaison Committee is supported by expert staff, and considerable preparation typically goes into a prime ministerial evidence session.

But, in the spirit of seeking to improve Brexit scrutiny, here are our suggestions for some Brexit questions the Committee could usefully ask on 20 December.

1. On what basis are you interpreting the wishes of those who voted Leave in the EU referendum?

2. Your October 2016 Conservative Party conference speech on Brexit had significant implications for the UK’s post-Brexit relationship with the EU. Have there been any such implications that you did not anticipate at the time?

3. Who did you consult before making that speech, and what material did you see in preparation?

4. Why did you decide on the end of March 2017 as your deadline for triggering Article 50?

5. What specific pieces of preparatory work for the negotiations did you ensure were done before you triggered Article 50?

6. When did you accept that talks with the EU on withdrawal issues and on the post-Brexit UK-EU relationship would take place sequentially, not in parallel?

7. For the record, can you confirm that the full Cabinet held its first formal discussion of the desired end-state for UK-EU economic relations on Tuesday 19 December 2017?

8. In June, the UK accepted the EU’s preference to sequence the negotiations into a phase one dealing only with withdrawal issues, before moving to transition and the future relationship. How, why and by whom was the UK decision to do so made?

1. Has anything surprised you about the Brexit negotiations so far?

2. Have you, or to your knowledge any of your ministers, sought information from third countries, or countries which joined the EU relatively recently, about their experiences of negotiating with the EU?

3. Are there lessons for Brexit to be learned from previous major all-of-government undertakings? If so, what are they?

4. To what do you attribute the government’s success in securing the EU’s agreement on 15 December that ‘sufficient progress’ has been achieved in phase one of the Brexit talks?

5. You set out at Lancaster House and in Florence, and in a series of government papers, a picture of a desired end-state UK-EU relationship; and yet there seems to be a perception, not least in the EU, that the government has not specified what it wants. Why do you think this is?

6. Have you learned any lessons in phase one of the Brexit talks that will cause you to do things differently in phase two, with respect to the government’s handling of the role of Parliament?

7. And, similarly, have you learned any lessons in phase one that will cause you to do things differently in future with respect to the devolved administrations?

8. Has the UK or the EU been the more transparent in its negotiating behaviour in phase one, or have they been roughly the same? In your experience, has the EU’s degree of transparency hampered its negotiating effectiveness?

1. Will the negotiations with the EU in phase two revert to taking place in pre-announced rounds, as they did in phase one between June and November?

2. For the record, could you set out the current roles in the Brexit negotiations of the Department for Exiting the European Union and the Europe Unit in the Cabinet Office?

3. How does the government plan to try to get the European Council (at 27) to adopt negotiating guidelines for the post-transition relationship in March that are as helpful to the UK as possible?

4. Will the government be tabling a formal paper to the negotiations on its desired post-transition economic relationship with the EU? If so, when, and what arrangements do you envisage for its parliamentary scrutiny?

5. You told the House on 18 December that you aim to have "details of our future arrangement with the European Union at the point at which we leave". Why do you think that this will be possible?

6. On what basis will the Cabinet be taking decisions on its desired post-transition economic relationship with the EU? What briefing have you requested to support Cabinet decision-making on this issue?

Fowler, B. (2017) Brexit questions for Theresa May and the Liaison Committee (Hansard Society: London)