A flag held high, a steely determination across her face: Her image epitomized the protests that electrified and paralyzed Paris in 1968 and now, aged 76, former model Caroline de Bendern is bringing her activist spirit to the streets of London on Saturday to fight to keep Britain in the EU.

De Bendern is concerned about the status of British nationals living on the continent, about Britain breaking away from the EU as Russia becomes more assertive, and about politicians' over-reliance on corporate finance. "The whole [political] system should be changed - that's what we wanted in 1968: change the system," says de Bendern, who was famously disinherited when her aristocrat grandfather saw the image of her amid the protesting leftists and workers on a magazine cover.

Caroline de Bendern was part of the '68 protests in France

The March to June 1968 protests began as "a student thing … people wanted more change, freedom," she told DW. By contrast, since the referendum, "extreme right-wing ideology has been gaining ground." De Bendern, who has lived in France since 1968, favors "a soft Brexit - if there has to be a Brexit."

Read: Thousands march in anti-Brexit protest in London

Tens of thousands of people are expected to take to the streets of London and Edinburgh this weekend for the Unite for Europe march to voice their opposition to Brexit. A spokesman for the Metropolitan Police said security would be increased at the march as it has been across the capital, following Wednesday's terror attack outside the Houses of Parliament.

Organizing committee adviser Roger Casale said he was confident the march would go ahead as planned. "I think we'll have more people than we were expecting. It's called Unite for Europe, but it's also Unite for Britain, Unite for London, and for all people of good faith. It'll be the first opportunity people will have had since the attack to show they stand up for values of freedom, diversity and equality, values that Europe stands for," he told DW.

The date - March 25 - was chosen to mark the 60th anniversary of the signing of the Treaty of Rome and it comes just before Prime Minister Theresa May officially triggers Brexit. Groups from all over the country are expected, united by locality or profession, such as Bristol4Europe or Scientists For EU. Casale said he wants the event to be family-friendly, "open and relaxed."

Not a march of millions

Spanish-born Carlos de Conde Solares, chairman of North East For Europe (NE4EU), told DW that initial claims that the marches would attract millions were "wishful thinking: we didn't have enough stewards." The 200 or so members travelling to the two marches from his group comprise mainly 20- to 45-year-olds "who almost took for granted that they were going to live in a continent with open borders and have seen their opportunities restricted."

Another protester, Hungarian-born Magdalena Williams, said Hungarians and Poles were "disappointingly" reluctant to march, fearing hostility. "Partly they're not used to protesting democratically, partly they're frightened, and partly they're working in jobs where they can't take the day off," she said.

Read: Pro-EU march in London as Gabriel calls for young Brits to be offered citizenship

Williams has been participating in a vigil that has been taking place three evenings a week for the last four weeks opposite the end of Downing Street. Many of her fellow-protesters come from other EU member states or have close ties to people who do. As well as cheerily waving EU flags at passing commuters and tourists, the few dozen protesters DW met had a PA system that played Beethoven's "Ode to Joy" and the Communards' 1986 hit "Don't leave me this way." The group's guitarist Peter Cook has also revised various lyrics: the Beatles' "Yellow Submarine" becomes "We all live in a dictatorship, a dictatorship, a dictatorship" - a reference to how Remainers feel that their concerns have been brushed aside.

However, participants are not united in what they are asking for, and this has been true even of the organizers of Saturday's march. The London march's slogan has changed from "Stop Brexit" to "Make your voice heard," and the event's originator Peter French abruptly resigned recently.

Pro-EU groups have been holding regular vigils outside Downing Street

"Don't mourn, organize"

"We're not asking anybody to 'stop Brexit,' that's last year's story," Casale said. To angry Remainers who still question the legitimacy of the referendum because it was only advisory, he says: "An act of Parliament has been passed." Just because Article 50 is triggered, doesn't mean Parliament must accept the final deal, he argues. Some protesters hope that the deal will prove too complicated to negotiate or be so unattractive that voters will pressure MPs to reject it.

One MP who will be addressing marchers in London on Saturday is Labour's David Lammy, who spoke in similar terms. "My message will be clear: 'don't mourn, organize,'" he told DW. "Nigel Farage wouldn't have given up the fight, so we have to fight for what we believe in when Article 50 is triggered and the impact of this hard Brexit at any cost begins to become clear [and] the wheels begin to fall off."

Read: EU fleshes out conditions for Brexit deal

Meanwhile, former Liberal Democrat leader Nick Clegg wants a second referendum, while Gina Miller, who successfully challenged the Brexit process in the courts, said she would return to court if she believed the correct process was not being followed.

Clearly the Remain campaign is still finding its feet, but needs to do so quickly to enable its followers to withstand the rhetoric of the Brexiteers. Emily Sawyer, 39, from East London, noted: "The Leave campaign has been campaigning longer than I've been alive and we haven't had time yet to really evolve yet as campaigns would, given time." At the end of Downing Street, Clive Lewis said his campaigning would not stop even once a deal were reached and Britain left the EU. "My motto is never, never, ever, ever give up."