The first theme to emerge was that the issues raised by the EU (Withdrawal) Bill are constitutional in nature. There was widespread agreement among the speakers that the UK is in, if not a constitutional crisis, certainly a constitutional moment.

The point was made most powerfully by Professor Colin Harvey of Queen’s University Belfast, who argued that the UK’s politicians, nations and publics should at least acknowledge that we are now having ‘a constitutional conversation’. Accordingly, he further argued that principles and values that are typically seen as underpinning effective constitution-making - such as consent, respect, rights and safeguards - should be engaged in the Brexit context. He held out the Good Friday settlement in Northern Ireland, with its many strands, as an example from which the UK as a whole might now usefully borrow.

Other speakers agreed about the constitutional nature of the EU (Withdrawal) Bill. Professor Mark Elliott of Cambridge University called the Bill in effect a ‘mini-constitution’; and Lord Lisvane, former Clerk of the House of Commons, called Brexit merely ‘the stage on which it’s happening’, while the issue is the nature of the constitutional settlement that the UK will be left with for coming decades.

However, several speakers contended that the UK (or at least Westminster) is poorly placed, conceptually and institutionally, to have Professor Harvey’s ‘constitutional conversation’. Professor Sionaidh Douglas-Scott of Queen Mary University of London regretted what she saw as the government’s tendency to frame the Bill as a purely ‘technical’ measure, apparently denying its constitutional nature – including in the event’s opening presentation by Daniel Denman, Director of Legal Advisors at the Department for Exiting the EU (DExEU). Professor Elliott was concerned by what he saw as the absence of any ‘constitutional concept’ at the heart of the Bill. Professor Dan Wincott of Cardiff University, chairing the panel on devolution, suggested that the UK had somewhat ‘backed into’ its current territorial constitutional arrangements, with post-1997 devolution followed through only weakly in terms of relations between the UK’s now-four executives and legislatures. As a result, few practised structures are in place to take the ‘constitutional conversation’ forward.

There was interesting discussion as to whether the public has any greater constitutional literacy and appetite than its politicians – particularly, as Michael P. Clancy of the Law Society of Scotland reminded us, in light of the popular engagement that took place around constitutional questions in Scotland during the 2014 independence referendum. Professor Menon reported hearing citizens mentioning ‘Henry VIII stuff’ during recent Brexit discussions. However, Professor Elliott wondered whether the UK lacks the kind of popular constitutional sensibility that might be found in some other countries; and Lord Lisvane worried that the unavoidably technical nature of some of the EU (Withdrawal) Bill issues would obscure for voters their constitutional import. He floated the idea of some body (perhaps a House of Lords Select Committee) compiling concrete examples of steps which ministers could take using the delegated powers in the Bill, to try to bring home their significance and help voters make sense of the political fights that will undoubtedly come as the Bill makes its way through Parliament.

As for the constitutional substance of the Bill, Edinburgh University’s Professor Stephen Tierney found it difficult to see how the Bill could have been drafted significantly differently. Daniel Denman openly and usefully laid out some of the choices that had had to be made during the internal government drafting process, and the rationale for the decisions made.

However, the balance of the contributions was towards constitutional concern. Professor Douglas-Scott got the event off to a provocative start by declaring that for her the Bill raised such fears for the constitution that it should not have received a second reading. Professor Elliott did not think that the Bill’s shortcomings could not be addressed through amendments, but he said that, as it stands, it ‘is an affront to the sovereignty of parliament, it eviscerates the separation of powers and it places the rule of law in jeopardy by compromising the principle of legal certainty’. Professor Elliott further suggested that the Bill raised the question of whether a measure can be lawful but unconstitutional.

Discussion across all our panels brought out specific constitutional implications of the Bill:

• On devolution, Dr Jo Hunt of Cardiff University argued that the Bill threatens to destabilise a Welsh devolution settlement which is not only already in flux but also ‘vulnerable’, because of the lack of guaranteed constitutional principles such as subsidiarity which might protect the ongoing move towards greater devolved powers. In Northern Ireland, Professor Harvey argued that Brexit overall was similarly destabilising, because it ‘reopens the sovereignty fracture’ in the province, and undermines the international context - involving the Republic of Ireland - which was a unique element of Northern Ireland’s post-1998 settlement.

• Inasmuch as rights are constitutional, the contribution from Martha Spurrier, Director of Liberty, reinforced the constitutional theme. Martha Spurrier argued that the EU’s Charter of Fundamental Rights awards rights over and above those in other instruments, such as the UN or European Conventions, and that the proposal in the Bill not to incorporate the Charter into post-Brexit UK law alongside other EU law thus constitutes a ‘regression of substantive rights’.

• The panel on the Bill’s delegated powers also came to focus on a constitutional question, of the balance between the executive and the legislature. Professor Elliott said that the powers the Bill proposed to give ministers were unparalleled, and Lord Lisvane suggested that they would have caused Henry VIII to be ‘very jealous’ (while the Bill caused Lord Lisvane himself to want to ‘lie down in a darkened room’). Michael P. Clancy reminded us that the powers in the Bill would affect the balance between executive and legislature in the devolved nations, as well as Westminster. Professor Tierney, speaking as part of the devolution panel, was concerned that the devolved legislatures might be especially weakly placed to exercise effective scrutiny of delegated legislation under the Bill, lacking both capacity in this area, and sight of the UK-EU negotiations.

• Several contributions suggested that, at Westminster, the relationship between Lords and Commons could also come into the picture. Lord Lisvane said that the accepted primacy of the Commons (but only this, not the nature of the Bill) meant that there was no question of the Lords rejecting the Bill at second or third reading. However, he expected the Lords to use its powers to require the Commons to ‘think again’, perhaps repeatedly, before the Bill is finally passed.

The second theme to emerge from the day’s discussions was the inverse relationship between trust on the one hand, and the demand for formal political institutions, on the other.

Several contributions in effect highlighted the fact that Brexit is triggering debates in which a lack of trust is prompting calls for stronger formal institutional arrangements:

• Daniel Denman stressed that no minister wanted to take delegated powers in the Bill that are broader than they need to be, or to use them for purposes other than the strictly necessary. He also argued that the powers had to be sufficiently broad that ministers using them – and business and citizens relying on the resulting law – could do so with certainty that there could be no grounds for legal challenge. However, Lord Lisvane contended that the issue was not the current government’s promises but a future government’s opportunities, and that Parliament would assess - and in all likelihood amend - the powers and their scrutiny arrangements accordingly.

• Professor Catherine Barnard of Cambridge University discussed options for the enforcement of post-Brexit rights where the EU so far does not appear content to rely on UK government assurances and UK-only mechanisms, and is insisting on the continued jurisdiction of the European Court of Justice.

• In the context of the weakness of the Sewell Convention (as set out in the Miller judgement), and a lack of trust of the Westminster government among its devolved counterparts (engendered by the former's handling of Brexit so far), Dr Hunt highlighted the Welsh government’s call for a new ‘UK Council of Ministers’. This would replace not only the current dysfunctional Joint Ministerial Committee but also, in effect, the EU Council, as a structure capable of bringing the UK’s four governments together in a joint decision-making process.

However, the contributions made clear that the sovereignty of Parliament cuts both ways in these debates.

Speakers who were concerned about the delegation of excessive executive authority in the Bill supported the idea that Parliament should assert its supremacy in UK law-making, by further circumscribing the Bill’s delegated powers and insisting on their better scrutiny. But Professor Barnard, and speakers on devolution, made clear that for the EU, and the devolved governments, the doctrine of Westminster parliamentary sovereignty is part of the problem, not the solution. It is precisely the idea that the Westminster Parliament can change almost anything that is prompting other Brexit actors to seek institutional and constitutional safeguards.

In light of the concerns raised during the day, it was perhaps not surprising that our final panel, of parliamentarians, presaged what Daniel Denman had already said he expected to be a 'bumpy but interesting' passage for the Bill in the UK’s legislatures. Stephen Farry MLA said that, if the Northern Ireland Assembly were reactivated in time, the political weight of nationalists there meant there would be 'zero chance' of it giving legislative consent to the Bill (although he expected the UK government would then overrule any such position). Eluned Morgan AM said that the Welsh Assembly would similarly decline to pass a legislative consent motion for the Bill in its current form. She raised the prospect of the Welsh Assembly passing ‘continuity’ legislation, to pass current EU law in devolved fields into Welsh legislation pre-emptively. This would, in effect, potentially dare the Westminster government to take the Welsh government to court. But, as a member of the House of Lords, Baroness Morgan also said that Peers were ‘licking their lips’ at the prospect of considering the Bill, and ‘clearing their diaries’ through January and February 2018. And, of the two MPs on our panel, not only Hilary Benn but also the veteran eurosceptic Sir Bill Cash appeared clear that the Bill would be amended, at least to address its delegated powers and their scrutiny. With the Bill's committee stage starting in October, Hilary Benn, Chair of the House of Commons Exiting the EU Committee, said that the government needed to understand that Parliament has 'absolutely no intention of being a bystander in this process'.