From the day we voted to leave the European Union, those most unhappy with the result have been intent on undermining that popular verdict's legitimacy by means of conspiracy theories.

These theories almost invariably involve claims of illicit financial string-pulling. The implication is that the British people, or at least those who voted for Brexit, are the unwitting dupes of nefarious financiers.

The latest — now being pushed by the Labour Party, the former Chancellor Philip Hammond and, believe it or not, Boris Johnson's sister Rachel — is that the Prime Minister's plan to achieve Brexit on October 31, Deal or No Deal, is part of a conspiratorial arrangement with 'hedge fund' financiers who allegedly stand to gain billions if the country 'crashes out' of the EU.

Rachel Johnson, in an interview on the BBC, criticised the Government led by her brother 'that is so keen to deliver Brexit in any shape or form'

Phillip Hammond is now claiming the PM's quest to leave the EU on the 31st of October is all part of wider conspiracy between him and 'hedge-fund' financiers

The claim is that there are a number of financiers who both back Boris Johnson and have made enormous bets on the pound crashing and stock markets falling. Further, that the Prime Minister is in league with, or manipulated by, these unpatriotic money-men.

Last Thursday, Rachel Johnson, in an interview on the BBC, criticised 'an executive' — that is, the Government led by her brother — 'that is so keen to deliver Brexit in any shape or form, to get the country out of the EU'.

Hostile

Asked who was behind this aggressive strategy, she replied: 'It could be coming from my brother himself … it could also be from — who knows — people who have invested billions in shorting the pound or shorting the country in the expectation of a No Deal Brexit.'

I'm not sure what Rachel meant by 'shorting the country'. I suppose she meant financiers taking bets that the share price of British companies will fall. She didn't explain how they might be influencing her brother in his policy, but the insinuation was clear.

Writing about the Prime Minister, Mr Hammond said: 'His sister has reminded us, he is backed by speculators who have bet billions on a hard Brexit

It was instantly taken up by Philip Hammond, one of the 21 MPs from whom the Conservative whip was withdrawn after they voted for what the PM calls 'the Surrender Bill', compelling the Government to beg the EU for yet another extension of our EU membership on whatever terms Brussels sets.

In an article for Saturday's Times, the former Chancellor, whose loathing for the Prime Minister is painfully obvious, wrote: 'Boris Johnson asserts, ever more boldly, that we will leave the EU on October 31, 'with or without a deal'.

'But as his sister has reminded us, he is backed by speculators who have bet billions on a hard Brexit — and there is only one outcome that works for them: a crash-out No Deal Brexit that sends the currency tumbling and inflation soaring.'

Among the necessary facts missing from Mr Hammond's article, which might have reassured us that he knew what he was talking about, are: the identity of these 'speculators'; the nature of their investments in full; and how, exactly, their portfolios stand to gain from (for example) 'soaring inflation'. Anyway, his claim was seized on by the best-selling novelist Robert Harris, who is profoundly hostile to Brexit.

Mr Harris tweeted: 'Philip Hammond, ex-Chancellor, seriously suggests that one reason the Prime Minister may want a hard Brexit is so that his backers in the City don't lose billions — corruption on a scale I wouldn't dare put in fiction.'

The Kremlin was accused of influencing the referendum via Facebook, without a shred of evidence

Sadly for those who want to believe in conspiratorial fantasies, this allegation of multi-billion-pound corruption of the PM by pro-Brexit speculators is fiction. But like most such conspiracy theories, it didn't just come out of thin air.

In fact, it comes from a recent article in a somewhat obscure new publication called Byline Times, which asserted it could 'reveal that currently £4,563,350,000 (£4.6 billion) of aggregate short positions on a 'No Deal Brexit' have been taken out by hedge funds that directly or indirectly bankrolled Boris Johnson's leadership campaign.

'Most of these firms also donated to Vote Leave … currently £8,274,350,000 (£8.3 billion) of aggregate short positions has been taken out by hedge funds connected to the Prime Minister.'

Oddly, the identities of these alleged 'Boris-backing, Britain-selling' hedge funds do not appear in the article.

Nevertheless, despite this omission — which no proper newspaper would regard as satisfactory in a so-called 'investigation' — the article went viral.

So viral, in fact, that its allegations were subjected to penetrating analysis in the Financial Times.

The FT absolutely loathes Brexit, and last week called on Boris Johnson to resign. But it roundly ridiculed Byline Times's widely circulated 'revelations'.

Benefit

To quote the FT: 'The inference is that hedge funds have used their financial might to influence the outcome of Brexit via political donations and are now standing to benefit from short positions in UK companies. The problem is, it doesn't make any sense.'

I won't detain readers with the full demolition, but among the points made was that many so-called 'UK stocks' might be quoted on the London index but 'have little exposure to the UK economy'.

None of these inconvenient facts has deterred Labour's Shadow Chancellor, John McDonnell, from demanding 'an independent inquiry' into the claims made by Mr Hammond.

For example, the Cineworld cinema chain, which, according to the data cited by Byline Times, experienced the most 'short-selling' in the past month, derives 75 per cent of its revenues from the U.S. If you wanted to maximise returns on bets that the UK would 'crash out of the EU', why on earth would you 'short' the stock of a company whose London-listed shares would rise if sterling collapsed?

In fact, any 'shorting' of Cineworld would effectively be a bet against No Deal.

As the FT concluded, this 'investigation' seized on so avidly by the opponents of Brexit is 'firmly in the realm of conspiracy theories'.

To rub it in, the UK's independent fact-checking organisation, Full Fact, also forensically demolished the central claim, under the headline: 'We think there's a big error in that viral article about hedge funds and Brexit.'

And Full Fact said that when they asked Byline Times to supply 'more information on which firms they consider to have been direct or indirect Vote Leave donors, they would not release this information'.

None of these inconvenient facts has deterred Labour's Shadow Chancellor, John McDonnell, from writing to the Cabinet Secretary Mark Sedwill, demanding 'an independent inquiry' into the claims made by Mr Hammond.

Sinister

And on yesterday's Andrew Marr Show, McDonnell's colleague Angela Rayner ran with the ball, declaring: 'What worries me is that speculators are going to profit off a No Deal, they are all backing Boris Johnson, and that's a conflict of interest.'

This conspiracy-theorising, masquerading as principled political argument, is just the latest — and I hope last — spasm of the campaign to prove that Brexit is the outcome not of democracy but of sinister subterfuge.

Angela Rayner accused Boris Johnson of a conflict of interest with speculators allegedly benefiting from a no deal Brexit

There was the claim that it was all down to Russian influence via Facebook: but while the Kremlin was undoubtedly keen on Brexit for its own reasons, there was never a shred of evidence that it had any influence on the outcome.

Then there was the claim, backed by the Electoral Commission, that a young Leave campaigner, Darren Grimes, had illicitly broken the spending cap in the last week of the campaign to the tune of £680,000. Amid much fanfare, he was fined £20,000.

But in July, a court upheld 25-year-old Grimes's appeal, finding him innocent.

Not Guilty: Both Darren Grimes (left) and Arron Banks (right) have been cleared of the wrong-doing they were both initially accused of, a nail in the coffin for conspiracies

In this context, we should never forget that far from the Leave campaign's victory being one of big money over the little man, the Remain campaign outspent Leave by £28.4 million to £13.4 million, once you include the £9.3 million spent by the then-Government on a pamphlet sent to every home telling us that leaving would be terrible 'for jobs and the economy'.

Then, last week, came the disintegration of the most treasured conspiracy theory of them all: that the largest pro-Brexit donor, Arron Banks, had broken electoral law with his contributions during the referendum.

Last Tuesday, the National Crime Agency announced that, despite lengthy investigation, it had found no evidence of such criminality on Mr Banks's part.

No wonder those campaigning to stop Brexit have moved on to a new conspiracy theory. The latest one is the loopiest of all: a true mark of their desperation.