Colleagues also noticed that the former Remainer had also shed some of his centrist views and was courting the Tory Right with a hardline message on immigration.

When we meet in his office a few yards from the Commons chamber, he insists he was not contemplating a tilt at the leadership at that point.

The Ozempic is long gone. ‘It worked, but it didn’t suit me,’ he says. But the weight has stayed off through exercise and ‘eating less’.

And his views on immigration have, if anything, got tougher. He has put leaving the European Convention of Human Rights (EHRC) at the heart of his campaign – and it is a key point of difference with remaining rival Kemi Badenoch, who wants to reform it – something he says is a ‘fantasy’.

If he wins through next month and makes it to No 10 in four years’ time, the Rwanda scheme will be back. And he makes a startling new pledge to kick out ‘all’ those living in the UK illegally – a plan which could see a future Tory government attempt to remove up to a million people.

On legal immigration, he promises a new annual ‘cap’ to limit numbers to the ‘tens of thousands’.

British businesses will have to find British workers to pick potatoes, clean offices and work in care homes and, if necessary pay them ‘a pound or more an hour’ to do so.

Mr Jenrick is painfully aware that the ‘tens of thousands’ figure was first promised by David Cameron in 2010, and that the Conservatives never got close to achieving it during 14 years in government – a failing he believes fuelled support for Reform UK.

His remaining rival is former Women and Equalities Minister Kemi Badenoch

Mr Jenrick delivering a speech at Policy Exchange, in Westminster, on Thursday

The tale of the tape ahead of the Tory leadership election – decided by party members at the end of the month

‘I share the anger and the frustration of the British public that this issue has not been taken seriously by politicians of all political stripes for most of my adult lifetime,’ he says.

‘And I am particularly frustrated that after we took back control of the levers of legal migration, upon leaving the European Union and ended freedom of movement, the ministers at the time made decisions which created a migration system even more liberal and open than the one we had.’

Yes, that is a swipe at Priti Patel and Boris Johnson, whose post-Brexit visa system, coupled with unexpected crises in Ukraine and Hong Kong, saw net immigration soar to a staggering 764,000 in 2022.

He also volunteers a dig at Liz Truss, describing her mini-Budget as ‘careless, cack-handed and un-Conservative.’

Mr Jenrick bridles at complaints that his relentless focus on immigration has made him appear a ‘one-club golfer’ – and reels off a string of policies on the economy, the NHS and defence.

‘On each of those issues, I have brought forward serious policy solutions,’ he says. ‘I don’t talk in platitudes. I’ve brought forward serious answers.’

On the NHS, for example, he says it is ‘time to stop treating it as a religion to be worshiped, but as a public service in need of reform’.

It is ‘a disgrace’ he says that 90 per cent of NHS trusts failed to remove a single manager for poor performance last year. ‘It’s incredible – name a business in this country that operates that way,’ he says.

On defence, he says he is willing to obliterate foreign aid spending in order to boost military budgets to three per cent of GDP.

But the conversation always returns to immigration, where he believes the contest is an opportunity to gain a ‘mandate’ from party members for tough action, including leaving the ECHR, which some moderate Tories are vehemently opposed to.

Critics within the party have questioned the sincerity of his conversion from moderate Remainer to right-wing hammer of immigration.

He acknowledges that his time in the office ‘did shape my politics, because I saw that the British state was just not performing its most basic duty, which is to secure our borders, keep people safe, and I concluded that I was not prepared to be just another minister or politician who would turn a blind eye to those problems.’

But he insists that in other respects ‘my values have always been the same’.

Those who doubt his sincerity might note that Mr Jenrick and his wife, high-flying corporate lawyer Michal Berkner, gave one of their daughters the middle name Thatcher long before he contemplated running for the leadership – a fact he now seems mildly embarrassed about.

‘It was her middle name. She’s going to turn out to be a socialist and resent this for the rest of her life,’ he jokes.

Mr Jenrick with his wife Michal Berkner – a high-flying corporate lawyer

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Mr Jenrick’s backers include heavyweight Brexiteers Sir Jacob Rees-Mogg (left) and Sir Bill Cash (right)

More seriously, he points out that he is backed by a string of heavyweight Brexiteers, including Sir Jacob Rees-Mogg and Sir Bill Cash.

Mr Jenrick has hinted heavily that his remaining opponent is something of a ‘drama’ queen, with a habit for getting dragged into ‘Twitter spats’ which risk taking the party down ‘rabbit holes’.

He stops short of attributing any of this directly to Mrs Badenoch, but says the choice facing Tory members is one between a ‘serious’ approach and ‘needless drama’.

Will he win? In this unpredictable contest, no-one can say. But if it is decided by effort and a sheer will to win then he stands every chance.

‘When the election was called, I was 66 to one – today this is a race which is neck and neck,’ he says.

‘Yeah, it could go either way. But people have been drawn to our campaign because we have a proper diagnosis of what’s gone wrong, and we’ve got real exciting, compelling policy arguments as to how we take the country and the party forwards. I think the momentum is with me.’