Brexit debates tend to be a mix of politeness and menace. Nearly five years since the referendum, the latest rematch didn’t disappoint.

I was amazed when Rudd and Mandelson resorted to ad hominem

The excuse was the launch of a book on the subject by Robert Tombs, but this wasn’t an ordinary book launch. Policy Exchange invited Lord (David) Frost, whom Boris Johnson has steadily promoted to leading interlocutor with the EU. The government’s other pre-referendum pro-Brexit representative was Michael Gove, whom Johnson recently demoted in order to add to Frost’s portfolio. This was the first time they have spoken together publicly since then. Gove has been vilified by both sides: too weak for Brexiteers, too strong for Remainers.

Gove had appeared with Tombs on the Brexit side of a farcical debate inside a stifling marquee during the heatwave of 2018. Back then, the other side was represented by Lord Adonis and Afua Hirsch, whose arguments always reduce to Brexit is racist, but we are children of immigrants.

Fortunately, Policy Exchange chose two Remainers who cannot claim the same: Amber Rudd (whom Boris Johnson sacked in September 2019 soon after inheriting Theresa May’s Cabinet); and Lord (Peter) Mandelson (whose Cabinet career ended with Gordon Brown’s defeat in 2010).

There are so many good arguments in favour of EU membership, so I was amazed when Rudd and Mandelson resorted to ad hominem. Leavers are unsophisticated and xenophobic said Mandelson. They’re sexist, said Rudd.

The Leavers on this panel did not bring these insults upon themselves. Tombs is a softly spoken, cautious, moderate speaker. He thanked the panellists for all comments, “nice or not so nice”. He challenged nothing.

Gove began his comments by admitting that “both options have equal validity and equal nobility.” EU membership offers transnational freedoms – particularly economic. But these advantages came with a democratic deficit. The EU offers economies of scale and collective power, but slower decision-making and more issue linkage.

Mandelson kept posturing as even-handed but complained that the government needs to be “more sophisticated” in its handling of Brexit; that “hard Brexit” has “jeopardised our trade position” and “our relations with the European Union are broken.”

In answer to a question later, he complained of “cutting ourselves off, separating ourselves, not being part of any international norm or convention, this sense of inward-lookingness, the whiff of xenophobia that we had from the leave campaign, [and] zero-sum British nationalism”.

Neither Rudd nor Mandelson had much to say about the book itself

Gove politely called out Mandelson for characterising Leavers as xenophobic. “We should leave that behind and better understand the arguments and impulses on both sides.” Mandelson jumped back in, with an expression somewhere between a Wallace-and-Gromit smile and a Pekinese snarl. He rephrased his whole statement as a caricature of the Leave campaign, but not leavers.

Gove responded simply with the ambiguous words of Charles de Gaulle to Algerian colonists in 1958: “Je vous ai compris” (“I have understood you”). Mandelson mouthed a self-satisfied “Thank you.” Either he didn’t understand Gove’s ambiguity, or he didn’t care to admit it.

Neither Rudd nor Mandelson had much to say about the book itself. Rudd, at least, didn’t seem to have read it. Mandelson started the hour by reading some words he had prepared in advance. He praised Tombs’ “vim and lightness of style” but bemoaned him as “a good man fallen amongst Conservative Brexiters”.

Mandelson complained that the book’s title (This Sovereign Isle) ignores Northern Ireland. Then he argued that “this hard Brexit” is weakening the Union. Circularly, “Northern Ireland can never work while we have a broken relationship with the European Union.” Indeed, he described EU-UK relations as “a vicious circle”.

Mandelson remained frustratingly contradictory and illusory on this issue, despite audience questions drawing him back to it. He said the government must abide by the Northern Ireland Protocol, just to reassure the EU that Britain is lawful. But (belatedly) he admitted that the EU must recognise that any border between Northern Ireland and Britain upsets Unionists. But while he urged compromise, he gave no hint as to how to reconcile the Union with an internal border.

The implication of Mandelson’s argument is that the government should not honour the majority of British voters

Mandelson’s alarm about the Union with Scotland was vaguer still. He wished that “ardent Brexiteers could recognise the tension that is being created between their belief in a pure Brexit which minimises our ties to our European neighbours, on the one hand, and the preservation of the Union of the United Kingdom, on the other.” He argued that because most Scots voted to Remain, Brexit alienates Scots. But the implication of his argument is that the British government should not honour the majority of British voters.

Mandelson jumped on an audience question to add that any separation from the EU’s human rights convention would help the SNP to win Scotland’s independence.

Gove said the government had no intention to separate from it and pointed out there are lots of reasons for Scottish separatism. But Mandelson wouldn’t stop banging on about Scottish and Northern Irish separatism.

One explanation is that he was Tony Blair’s Secretary of State for Northern Ireland. (The other panellists good-naturedly praised him as a good one.)

Another explanation is that he was spinning. (He was Tony Blair’s spin doctor, after all.) Mandelson blames the British government for jeopardising the Union. But the EU insisted on separating Northern Ireland from the rest of Britain before it would negotiate the Withdrawal Agreement. And the EU is inventing reasons why the border between Britain and Northern Ireland should be harder. Tombs had the last word: the Union will be stronger outside the EU.

Mandelson’s prescriptions for the future EU-UK relationship were characteristically platitudinous: “We have to reinvent ourselves or face national decline … We either fall apart or get our act together … replacing [the EU’s] weight with [national] nimbleness … successful externally only if we are successful internally … major bold strategic moves…” Everybody agreed.

Mandelson had welcomed Frost as a “new colleague in the House of Lords”. Frost cleverly thanked Mandelson, then said “I look forward to debating him across the floor of the House.”

Frost agreed with “the need for renewal and moving forward”. However, Frost respectfully disagreed with Mandelson’s “dismissive caricature of a hard Brexit”. Mandelson “misses the fact that a soft Brexit means other people set laws we have to live by. And I still don’t find a satisfactory [argument for] the proposition that for part of our national life we should abide by laws over which we have no control.” Brexit is “the logic of democracy”.

Back when a civil servant, Frost realised that European membership “had a kind of sapping quality to our ability to take decisions”. Britain descended into “institutional paralysis and learned failure … well beyond the areas within EU competence”. He looked forward “to get a grip, to reform the state, to reform our own attitudes, to become a country that can deal with problems again”.

Tombs had explained that women were likelier to vote Remain because they are more risk averse

Rudd started her comments by unguardedly admitting that she is more prejudicial since leaving politics: reading only what she agrees with; following on Twitter only whom she agrees with. She resented agreeing to read Tombs’ book. She complained it is “very much a leaver’s book” (duh!). Her final prepared comment was sarcastic and hypocritical: she wished Tombs had written “an equally interesting book putting the case for Remain, but then, what a ridiculous idea: two articles or two books, arguing for different points of view!”

Rudd said that some of the book “was so tribal I was laughing out loud”. This is the sort of comment that suggests she hadn’t read the book.

Her only evidence for Tombs’ “tribalism” is that Tombs had explained that women were likelier to vote Remain because they are more risk averse. Rudd didn’t explain how gendering an issue is the same as tribalism. I suspect her error was confirmation bias. She recalled “a slight feeling that this [Brexit] was a man’s project … a group of men having a man’s comradely endeavour”. Since 2019, “Boris Johnson’s government has continued with that.” Her evidence? Only 20 per cent of his Cabinet is female. For her, this gender imbalance is “a continuation of the Brexit campaign”. Then she admitted that she was being tribal.

She said Tombs did not “give credit” to a “really soul-searching time [in Theresa May’s Cabinet] … when we were desperate to find a compromise … honest, earnest, and desperate … to find a peaceful resolution, as the crowds outside Parliament stoked up further and further”. She hoped Gove would endorse her recollection. He did not.

Rudd said she “long[s] for the day that we can talk about Britain’s success or failure in the new regime without having to continually label Remainers or Leavers as though it was a sin to be on one side or the other. I hope the government will help us do that.”

After her prepared comments, Rudd was largely irrelevant. Lots of negative reaction rolled through the chat box. The host chose to ignore audience requests to ask her questions, and he chose not to redirect other questions her way.

One of the final questions was about how much longer we would be debating Brexit. Rudd followed one of Mandelson’s answers by pondering why the last five years were so bitter. The clue is in the way she framed her question: Brexit took nearly five years. And she was one of those who frustrated it.

If this is the state of political debate nearly five years on from the referendum, then how many years, and how many scholarly books like Sovereign Isle will it take to settle our relationship with the EU and ourselves?