During the febrile, topsy-turvy days after Britain voted to leave the European Union, there were plenty of tough messages from European leaders. But few sounded more uncompromising than the EU trade commissioner.

A week after the result, Cecilia Malmström, Europe’s lead trade negotiator, stated that the UK could not even begin discussing a trade deal until it had left the bloc. “First you exit and then you negotiate the terms of the relationship,” she told Newsnight, opening up the prospect of the world’s sixth-largest economy being left dangling for years. When the BBC interviewer suggested this would damage businesses in Britain and on the continent, her response was straightforward: “Yes, but the vote was very clear.”

Such plain speaking provoked fury among leading Brexiters. Conservative MP Liam Fox condemned her remarks as “bizarre and stupid”. While legally correct that Britain cannot sign a trade deal before it has left, by taking such a tough line against early negotiations, she walked into a political minefield.

In a few months’ time, Fox, since appointed Britain’s secretary of state for international trade, may find himself sitting opposite Malmström. Nobody knows exactly how big a role the 48-year-old Swede will play in Brussels’s team Brexit. Michel Barnier, the silver-haired former French foreign minister, has been given the task of leading Brexit talks by European commission president Jean-Claude Juncker. Meanwhile, Belgian diplomat Didier Seeuws is handling Brexit for his boss, European council president Donald Tusk. Another EU president, Martin Schulz of the European parliament, is unlikely to stay quiet, as MEPs have a vote on the UK divorce and any subsequent trade deal.

If the cooks are in Brussels, the master chefs are in Berlin, Paris and other national capitals. Anyone negotiating a future EU-UK trade deal is going to find many political leaders looking over their shoulders, says Fredrik Erixon, director of the European Centre for International Political Economy. The British deal will not be a normal trade negotiation, akin to Vietnam or Canada, he stresses. “Member states are going to play a far more prominent role in defining the ambitions or the objectives of where these negotiations land.”

Meanwhile, the Swedish commissioner has plenty more on her plate: she wants to conclude a deal on the Transatlantic Trade and Investment Partnership, better known as TTIP, the most controversial trade deal the EU has ever negotiated. Talks will reach a moment of truth in the autumn as both sides strive for an agreement before President Barack Obama leaves office.

But doubts are mounting about whether a deal is possible. To critics, TTIP is a charter for deregulation that threatens the NHS. EU and US officials say the reality has become buried under myths and strenuously reject charges of secret negotiations.

“She is very open and transparent in what we are doing,” says one EU source close to the commissioner, who cites Malmström’s decision to publish EU negotiating positions after the talks. “We have taken transparency quite far. It is not on our interest to take it much further because we would be bad negotiators.”

Facebook Twitter Pinterest Liam Fox, now Britain’s secretary of state for international trade, was incensed by Malmström’s comments on Newsnight after the Brexit vote. Photograph: Andy Rain/EPA

Although not exactly unusual, the volume of criticism is a far cry from Malmström’s early political days. As a member of the European parliament between 1999-2006, Malmström was a hero of the liberal left, known for taking a firm stance against sweeping data-retention proposals.

She was one of the “warrior parliamentarians” in the parliament’s liberal group, recalls Teresa Küchler, a reporter at Swedish daily Svenska Dagbladet. “When she became a commissioner, everyone thought she shut up very quickly,” she says, noting how carefully Malmström avoided criticising decisions taken by EU governments. Cautious maybe. But not a dry-as-dust technocrat, who floats above politics. “She is known for being a liberal, above all, with not a drop of conservatism in her,” Küchler adds. Mats Karlsson, director of the Swedish Institute of International Affairs, describes her outlook as the politics of the “decent middle”, the big tent of Swedish Labour and centrists who came of age during “the golden age of globalisation and Europeanisation”.

Malmström is also a true European. She was born in Gothenburg, Sweden’s earthier second city, home to Volvo and Swedish manufacturing. Swedes can hear this in her accent, the Gothenburg lilt associated with banter and down-to-earth common sense. “Even if she had been a politician for 100 years, she still comes across as a local, clever woman that we can be proud of,” says Küchler, a fellow Gothenburger.

Like so many Swedes, Malmström speaks impeccable English. She is fluent in French and Spanish, comfortable in German and Italian. She spent part of her childhood in France and completed a PhD in Catalan and Italian regional politics. She studied literature at the Sorbonne in Paris and is as likely to have the latest Elena Ferrante novel in her bag as she is the TTIP text on public procurement rules.

After stints as a Gothenburg town hall official and political science lecturer, she was soon climbing the ladder of Swedish politics, elected to the European parliament in 1999, aged 31.

Like her friend and fellow liberal Nick Clegg, a career in the European parliament was a springboard into national politics. But, in Malmström’s case, not for long. After four years as Europe minister in Sweden’s liberal centre-right coalition, she returned to Brussels as Sweden’s European commissioner. She was put in charge of home affairs, a demanding portfolio covering asylum and terrorism that makes, but mostly breaks, reputations. This was a difficult job. Every year, more people were setting off in rickety boats from north Africa hoping to reach the Italian island of Lampedusa. Every year, more were dying. In October 2013, disaster struck. At least 366 people drowned less than half a mile from Lampedusa when their overcrowded fishing boat capsized. As EU commissioner, Malmström urged governments to do more. Italy set up the Mare Nostrum search-and-rescue operation, which was credited with saving 400 lives a day, although operations were later drastically scaled down. But she was far less successful in persuading EU countries to share responsibility for refugees, a divisive issue which has only grown more rancorous.

Malmström returned to Brussels for a second term, under Juncker, and took over EU trade policy, amid growing scepticism about big corporations in the wake of the economic crisis.

Karlsson thinks his compatriot will be clearly focused on European interest when it comes to Brexit. “I think she will be a very hard negotiator in that we did not create this problem, this was a problem created by Britain.”

Reflecting a fairly widespread view among pro-European Swedes and beyond, he said: “Britain can only get a bad deal, a very bad deal ,or a catastrophic deal. I think that she will be very clear about what is required.”