Covering the Greek crisis for BBC Newsnight in 2015 meant spending long days in a very hot Athens, eating too much room-service kebab and trying to stay on top of a series of twists and turns in Greek and European politics while all the time keeping an eye on the financial markets. The fundamental question was: will Greece do a deal or will it crash out of the euro?

At the time, I had no idea that my crash course in European standoffs would prove useful to understanding what has emerged as the key question in British politics, Brexit: deal or no deal.

On the first day of the Boris Johnson government, the emergence of former Vote Leave strategist Dominic Cummings in the role of senior adviser in Downing Street was taken to be more significant than any cabinet-level appointment. There’s a long tradition of talking up backroom operators in British politics, from Alastair Campbell in the 1990s to Nick Timothy under Theresa May, but, to me, the most striking parallel is with Greece.

Although I imagine neither man would welcome the comparison, Cummings now seems to be playing the role of Yanis Varoufakis, the Greek finance minister in 2015. Cummings’s hardline approach to negotiations with Europe echoes that of Varoufakis. Like his counterpart in 2015, Cummings is in favour of pressing ahead with no-deal planning in order to secure a deal. And perhaps like Varoufakis in 2015, Cummings’s interests are not fundamentally aligned with those of the prime minister he serves. The point may come when Cummings has to be ditched.

Both men are outsider insiders with no deep attachment to the party they work for. Varoufakis spent his working life in economics before being appointed finance minister, while Cummings has never been a member of the Conservative party. Most importantly, both have a sense of mission that is bigger than any individual prime minister, government or party. For Varoufakis, ending austerity in Greece was the goal, and he was prepared to risk slipping out of the euro to achieve it. For Cummings, exiting the European Union has been something he has spent the best part of 25 years trying to achieve.

Facebook Twitter Pinterest ‘For Cummings, exiting the European Union has been something he has spent the best part of 25 years trying to achieve.’ Dominic Cummings in Whitehall. Photograph: James Veysey/REX/Shutterstock

During his five-and-a-half-month stint as finance minister, Varoufakis’s strategy was premised around preparing Greece for a euro exit in order to win concessions from its creditors. The theory, and Varoufakis is a game theorist by background, was that a so-called Grexit would raise fundamental questions about the long-term future of the single currency. Once one member state had found the exit door, markets would begin to ask who was next, and the government debt of the rest of the “European periphery” would begin to fall in value. The very threat of leaving, he hoped, would force Greece’s lenders to relax the terms of their loans.

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That strategy failed for two reasons – first, the markets decided that 2015 was not another systemic euro crisis but rather an idiosyncratic “Greek crisis”. No matter how close Greece wandered to the cliff edge, it did not look like Portugal, Spain or Italy would follow. So rather than threatening mutually assured economic destruction, Varoufakis looked to be threatening just a Greek implosion. But domestic politics in Greece mattered just as much. When push came to shove, The Greek prime minister, Alexis Tsipras, was not prepared to back his high-profile consigliere. He had been happy to allow him to front up the high-risk strategy until the last moment, but when it became clear that threatening the Greek equivalent of a no-deal Brexit had not won concessions Varoufakis was dropped like a stone.

For the moment, Johnson’s and Cummings’s interests are aligned. Ramping up no-deal preparations while making clear that a “clean Brexit” is a workable option both helps contain the Brexit party vote share domestically and might help wrangle some minor changes out of Europe. But those interests could diverge very rapidly.

Faced with at best a sharp economic slowdown and at worst serious fuel shortages in November, Johnson’s threat of a no-deal Brexit may appear to be as firm as Tsipras’s threat of a Greek euro exit in 2015. In which case Cummings would quickly go the way of Varoufakis.

• Duncan Weldon is an economist, writer and broadcaster