Boris Johnson may be the most powerful UK prime minister of modern times but “political tensions remain” and “the drama isn’t over”, corporate travel leaders were told this week.

Political commentator and broadcaster Steve Richards told a Global Business Travel Association (GBTA) and Institute of Travel Management (ITM) symposium in London: “The questions of the last three years have not been answered.”

He warned corporate travel leaders: “It’s going to be very difficult to get beyond a cosmetic [Brexit] deal. Some of your concerns will not be fully worked through.”

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Richards argued: “Boris Johnson is currently the mightiest prime minister of modern times. [But] political honeymoons are deceptive.

The “seeds of future problems are being sown”, he said: “There are many tensions. The drama isn’t over.”

Richards told the symposium: “Some compare Johnson to Tony Blair in 1997, but Blair was never as powerful – at the Treasury he faced [then Chancellor] Gordon Brown. Blair didn’t know what would be in a Budget. The Budget next month will be written by Number 10.”

The tensions in the UK government surfaced during a cabinet reshuffle on Thursday when Sajid Javid resigned as Chancellor after refusing to sack his political advisors and was replaced by Rishi Sunak.

Javid had only been in the job six months and was poised to deliver his first Budget in March amid behind-the-scenes rows over Treasury restrictions on government spending.

Richards suggested: “Boris Johnson faces really tough decisions. [The go ahead for high-speed rail] HS2 angered a lot of Tory MPs. Theresa May could not have taken that decision.

“Boris is a genuine fan of infrastructure, but how the hell does he pay for it? He is preparing a Budget that has to balance pleasing former Labour voters in the North with satisfying Tory voters in the South.

“Then there are the trade talks with the EU. Boris wants divergence. He says he wants free trade but implies Britain will become protectionist in relation to its biggest market.

“The EU knows what it wants and it’s probably closer to what the travel industry wants.”

Richards warned: “There is not even a year left for trade talks. They won’t begin until March. The EU takes the whole of August off and quite a bit of July and September.”