Mr Cummings, a fierce critic of the Foreign Secretary, took to Twitter last week to suggest, without providing evidence, that her campaign was “being run by Jason Stein & Roland Rudd, literally the most ‘Remain and Rejoin’ campaigner in UK”. Mr Rudd is the founder and chairman of FGS Global, formerly RLM Finsbury, a PR company, where Mr Stein also works.
The brother of former Home Secretary Amber Rudd, Mr Rudd was until 2019 chairman of the Open Britain campaign, one of five organisations underneath the People’s Vote umbrella which pushed for a second referendum.
Mr Stein is himself a former adviser to Ms Rudd, and also “managed all communications” for Ms Truss when she was Chief Secretary to the Treasury, according to his LinkedIn page.
The insider, with knowledge of the Truss campaign, said while they were unaware of either Mr Rudd or Mr Stein formally part of Ms Truss’ team, it was “plausible” that they were offering advice in an informal capacity.
They told Express.co.uk: “If it’s true, I think it is a sign that we have moved on from the Leave-Remain split.
“Sure, there are a handful of Remainers like the Japanese soldiers still fighting World War 2, but for the overwhelming majority, Brexit is now a fact, not an opinion.
“That’s how Liz treated it from the moment the referendum result was known.
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Three months later, she told the Food and Drink Federation, she said: “If we are a country like Norway we would have to fill in 50 boxes on a form every time we wanted to export something.
“We’ve got to be very careful about taking that single market for granted & being outside that single market.
“The single market is really crucial to the amount of growth we’ve seen in food and drink exports.”
However, earlier this month, she told the BBC she had changed her mind.
She explained: “I fully embraced the choice that the people of Britain have made.
“I was wrong and I am prepared to admit I was wrong.
“Some of the portents of doom didn’t happen and instead we have actually unleashed new opportunities.”
Her opponent Rishi Sunak, the former Chancellor, attempted to capitalise on her previous stance during a debate on ITV on July 17, during which he asked her: “You’ve been both a Lib Dem and Remainer. Which one do you regret most?”
Express.co.uk has contacted both the Truss campaign and Finsbury FGS for comment.