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Yet, bar an early and explosive two-part joust with the former leader of UKIP Nigel Farage, the former deputy prime minister played a relatively peripheral role in the immediate run-up to June 23.
He generally confined his campaigning to a local level, knocking on doors and dispensing leaflets in his Sheffield constituency, while letting others hog the national limelight, despite being one of the most vocal and well-known Europhiles in Westminster
"My immediate political history was obvious," the former leader of the Liberal Democrats said when we sat down with him on Wednesday morning. "I'd resigned as party leader and been ejected from office. I didn't seek a prominent role nor did I think it would be right to give me a prominent role."
"The timing was the issue. The referendum took place quite shortly after my government and leadership career had met a fairly abrupt end. I'm not a master of the timing of these things. I wasn't in the strongest position to man the barricades. I did what I was asked to do but didn't seek anymore."
Rebuilding the Liberal Democrats after a party collapse
Clegg resigned as leader in 2015 after witnessing the party collapse at the general election.
The Lib Dems lost 49 seats, having served as the junior partner in the David Cameron-led coalition government. Now, the Sheffield Hallam MP is watching on as his successor Tim Farron attempts to revive the party, its new lifeblood being disgruntled Remainers who feel lost in a party system dominated by a Conservative party determined to deliver Brexit and an opposition struggling to settle on a view about Britain's future outside of the EU.
The party's MPs have vowed to vote against Theresa May blocking Article 50 unless she guarantees a second referendum, this time on the terms of Britain's departure. We suggested to Clegg that trying to block the Article 50 process is neither liberal nor democratic, an accusation he was keen to "flip on its head" and rebuff altogether.
"I think it's impeccably democratic because it would be the first referendum which would allow the people to pass a judgment on what Brexit actually means. I think it's very undemocratic to assume people should simply accept what they're given by the government of the day following the conclusion of a negotiation of which at present we know nothing about and which the government appears to be utterly clueless about.
"If the Brexiteers had spelled out in any detail what they meant by Brexit then I would have some sympathy with the idea that not only have they got a mandate to take us out of the European Union but also a mandate on how to do it," he added.
"It's undemocratic to not give the British people a say at the end of the process just as much as they've been given at the beginning of the process."
"But they've very deliberately and very cynically withheld from the British people any description of what it means in practice. I'd flip it on its head. I'd say it's undemocratic to not give the British people a say at the end of the process just as much as they've been given at the beginning of the process."
May's government continues to enjoy double-figure leads over the Labour in the opinion polls, despite ongoing cabinet fall-outs and continuing uncertainty about her plans for Brexit. However, Clegg believes they are heading for trouble.
"I think this government is one of the most clueless in living memory," Clegg says.
"Theresa May's quite methodical manner and demeanour give an impression of the government somehow knowing what it's doing but I think they are at sixes and sevens. It's one of the most clueless governments I've ever seen.
"They talk to each other and to the media as if all they need to do is resolve the differences around the cabinet table but that's only the first little baby step. They soon have to negotiate with 27 other countries and 27 other parliaments that have their own needs and their own objectives.
"There is this extraordinary hubris in Westminster and Whitehall that all is needed is like when white smoke comes from the Vatican when a pope is anointed to pronounce to the world from her bunker in Number 10. But this is a much more complex, Rubik's cube of negotiations with 27 other countries, and so far I've seen no evidence at all that this government is even vaguely aware of quite how complex and contorted this negotiation can become."
"It's intensely embarrassing having this mop-haired buffoon as our foreign secretary"
He reserves particular ire for the foreign secretary Boris Johnson, who he believes is damaging Britain's name on the world stage. The outspoken Brexiteer has aggravated a number of his European counterparts since taking up the position, not least for his contradictory statements about Turkey joining the EU.
"It's intensely embarrassing having this mop-haired buffoon as our foreign secretary, who thinks it's okay to frighten the living daylights out of the British people by claiming 80 million Turks could turn up at Dover if we were to remain in the EU and then without the slightest smidgen of embarrassment fly off to Ankara and say to the Turks 'welcome to the EU!' It beggars belief. I've never seen such unashamed and two-faced posturing.
"I think it doesn't serve the country very well at all because it leaves people at best amused and at worst completely lost on what the intentions are of this government and our country. It's as if we've taken this great leap in the dark and the pied pipers - Gove, Farage, Johnson, and so on - who successfully won the argument, don't seem in the slightest bit responsible or bothered to try and explain what happens next."
Darren Staples / Reuters
One of the issues at the very heart of the EU debate was immigration.
The Leave campaign declared Brexit would allow Britain to "take back control" of its borders by slashing the number of people entering from the 28-nation bloc. The prime minister has vowed to prioritise restricting immigration in Brexit talks but has been warned by figures like Guy Verhofstadt - the EU parliament's chief Brexit negotiator - that ceasing to accept the free movement of people will cost Britain its single market membership.
Surprisingly Clegg doesn't believe the negotiations will hinge on immigration. In fact he believes the issue of free movement could be more flexible than the likes of Verhofstadt have suggested.
"It's just not true to say that the free movement of people is some biblical principle since the dawn of time. That's not the case. The freedom of movement doctrine has evolved over time, not least since the creation of EU citizenship and numerous court cases since. And, crucially, there is profound concern in other countries about immigration generally. It would be very naive of Verhofstadt or anyone else to claim that the European public is unconcerned about immigration because that's just not true. Any democrat anywhere in Europe should acknowledge that the very large scale movement of people across the continent is unsettling a lot of voters.
"Any democrat anywhere in Europe should acknowledge that the very large scale movement of people across the continent is unsettling a lot of voters."
"If Theresa May was smart on this, which she isn't being, she would try to meet the EU half-way on this. I think there is a meeting point between the very large concern in some parts of the EU about immigration from elsewhere and British concerns about internal immigration in the EU. I think you can make a package that addresses both concerns.
"I think the biggest problem is May's fatwa against Britain abiding in any way with the single market and the European Court of Justice. That places Britain between a rock and a hard place. You cannot have maximum access to the single market free of bureaucratic impediments if you're not prepared to play by the rules. It's a marketplace of rules. It's simple - abide by the rules or don't.
"It's amazing. Everybody intuitively understands you can't wander into a golf club and get all the benefits of the membership without paying a fee and abiding by the rules. Yet the idea that you can get a free lunch at the club without abiding by the rules is nonsense. The exact same applies to the EU. Boris Johnson merrily says we can have our cake and eat it - but of course, we can't."
Working with former Prime Minister David Cameron
It was Clegg's former colleague David Cameron who decided to hold a referendum on Britain's EU membership.
It was a miscalculation of Shakespearian proportions that led to a political earthquake in the UK and his resignation both as prime minister and Tory leader.
"His legacy will be defined almost entirely by that spectacular misjudgment to hold the referendum as a ploy to placate the divisions within his own party ... It's a pity for him," Clegg said.
But, as we sit in his central London office, he admits that he still retains a great deal of admiration for his former colleague. "He was a really good coalition prime minister," Clegg said.
[Cameron's] legacy will be defined almost entirely by that spectacular misjudgment to hold the referendum.
"He was a pretty poor and rubbish Conservative prime minister. Even before the referendum, he and Osborne seemed unable to do anything right. When they were left to their own devices and free of the constraints of coalition they screwed up. They were incompetent the moment they finally got the prize that they'd always longed for.
"But as a coalition prime minister, which is a difficult thing to do, as is being a deputy coalition prime minister, he was really good. He was supple, he was flexible, he was good at trying to find accommodation between the two sides.
"The tragedy I always felt about his position was that he could never admit to his own side and to the barking mad folk at the Daily Mail and elsewhere that he actually quite liked being coalition prime minister. They could never admit to the indignity of enjoying sharing power. If he had made a virtue of that it would have highlighted his strengths - which as a coalition leader were really quite considerable."
But, the former prime minister's qualities aside, it will be always his decision to bow to the pressure of "obsessive" Tory Eurosceptics that will define his place in history, Clegg added. "One of the great myths perpetuated by the Brexit press is that there was a widespread popular public clamour for a referendum. Absolute rubbish. Even at the height of European controversies, the EU barely scratched its way into the top ten of public priorities. It was an absolute obsession for a political clique in Westminster and amongst their supporters in the press."
How the Liberal Democrats are gaining ground
The Liberal Democrats' strategy of appealing to the 48% appears to be working. In recent by-elections in Remain constituencies Witney and Richmond Park, the party increased its share of the popular vote by over 20%.
In the latter, Sarah Olney pulled off a stunning victory, winning 23% of the vote from former Tory Zac Goldsmith. If the party can target Remain seats where its biggest rival is the Conservative Party with the same effectiveness, then up t0 20 seats could be up for grabs at the next election, giving rise to the possibility of another coalition government.
Farron hinted earlier this year that he would be willing to take the Lib Dems back into a coalition government if the opportunity arose, despite the electoral disaster that awaited the party after its role in the most recent coalition.
Clegg echoed the comments of his successor, suggesting the party had a duty to seize power if given the chance.
Eddie Keogh/Reuters
"I think what Tim was saying quite rightly is that the point of being in politics is not just to throw stones at your opponents - it's to do stuff. If you have the opportunity to do stuff then you should think hard about doing so," he says.
"Politics isn't about academia. It's rough old business where the prize is to change the world where you see for the better. You can only do that if you're prepared to get your hands dirty and exercise power. It'd be foolish of Tim to rule out an appetite to do stuff."
"Progressive alliance" is a buzz-phrase in British politics at the moment. With Labour looking unlikely to form the next government, some people favour parties of the left developing a collaborative strategy in order to keep May's party out of power. This would involve parties stepping aside in certain constituencies to make it easier for another 'progressive' party to win the seat.
"There is a chronic need for non-conservative parties to apply proper scrutiny and accountability to government that only secured less than a quarter of the public vote," Clegg told us. "But how that cooperation comes about I find much more difficult to predict."
"Labour can never wield power again without sharing power again."
"Oddly enough, I don't think the question [of a progressive alliance] should be directed at the Liberal Democrat - but the Labour Party. Until the penny drops in Labour, it can never win again under the present arrangements. As long as the Scottish nationalists dominate Scotland Labour can never win again. Labour needs to have a dark moment of the soul where it asks itself what is it in politics for. Labour can never wield power again without sharing power again.
"If the Labour Party get that, which they clearly don't at the moment, then conversations could start."
There was some talk of Clegg quitting politics altogether after witnessing his party collapse. The MP looked deflated and defeated when he announced his resignation as leader, but he believes it would have been wrong to "flounce off prematurely". There is a strong chance that this parliament will be his last, though, with a decision yet to be made on whether he'll stand at the next general election.
"I've been an MP for 11 years and I've been in politics a lot longer than that. I'm about to turn 50. Do I want to spend my whole fifties carrying on in politics?
"I will tell my constituency party before I tell anybody else having made up my mind in the next year or so.
"At the moment, I'm just happy to play my role as I did in the Richmond by-election and helping Tim recover the Liberal Democrats. Most importantly, I want to speak up for a liberal, internationalist, engaged Britain that I think is severely under threat at the moment. I'm happy to do that for the time being."