Even the most cursory list of Europe's best-known actors reveals a continent stocked with starry talent: Ewan McGregor, Jude Law, Kate Winslet, Judi Dench and Helen Mirren from the UK; Eva Green, Isabelle Huppert, Daniel Auteuil and Juliette Binoche from France; Monica Bellucci and Roberto Benigni from Italy; Franka Potente from Germany; and from Spain, Antonio Banderas, Javier Bardem and Penelope Cruz.

But the international renown of these actors belies a perennial problem for European film-makers, distributors and sales agents: how best to capitalise on local stars to create projects that gain visibility at the box office and international sales'

At a time when stars are more crucial than ever for getting bigger budgeted movies financed and made, the question of what constitutes a star - and what they are worth - has become even more difficult than ever.

While certain European actors may command major salaries in Hollywood pictures, their worth when it comes to European projects is complex. And the fact remains that European talent can rarely greenlight a movie - even in Hollywood. Casting director John Hubbard, whose credits include The Da Vinci Code and King Kong, says that even the highest-profile British actors cannot open a movie in the US.

A major problem, suggests international PR consultant Lucius Barre, is the continent's sheer cultural diversity. Stars may achieve huge fame and popularity in their own country but can struggle to reach any level of recognition elsewhere. The lack of European films playing widely outside their home territories compounds matters further.

'Real stars only come from the UK, France, maybe Spain.'
In recent years, initiatives such as European Film Promotion's Shooting Stars programme (which celebrates its 10th anniversary at this year's Berlin International Film Festival) and the European Film Awards have sought to promote young European talent and to help it travel across national boundaries. Nonetheless, it remains highly debatable whether there is a European star system as such.

'There are only a few territories that have produced stars that have become household names outside their local market,' notes Christian De Schutter of promotional agency Flanders Image. 'The only real European stars originate from the UK, France and maybe Spain.'

The Weinstein Company's Colin Vaines argues that the European stars who really flourish are often those who 'don't abandon their roots' but instead go backwards and forwards between the Hollywood system and Europe. Penelope Cruz, Oscar nominated this year for Volver, is a prime example of an actor who has managed to combine working in the studio system with a European career.

Casting agents for international productions remain interested in European talent, starry or not. French actor Gaspard Ulliel, for example, was unknown when cast in Hannibal Rising. 'That was a huge gamble to take but in my view, it was brilliant because he is fantastic in the film,' says The Weinstein Company's Vaines.

'When we tested the film in North America, there was no issue about 'is this a French actor'' or 'who is he''. People just accepted him as a young Anthony Hopkins.'

The programme of the 2007 Berlinale is also testament to European actors' ability to travel, with a host of stars appearing in films made outside of their own territory or with foreign directors. These include Romola Garai in Francois Ozon's Angel, Gerard Butler in Zack Snyder's 300, Moritz Bleibtreu in Paul Schrader's The Walker and Martina Gedeck in Robert De Niro's The Good Shepherd.

There have always been plenty of European stars: actors who flourished both in their local markets and internationally. Whether Greta Garbo or Marlene Dietrich, Charlie Chaplin or Ronald Colman, Europeans prospered in Hollywood during the classic studio era.

In the post-war years, with Neo-Realism in Italy, the Nouvelle Vague in France and Free Cinema in Britain, a new generation of 'auteurs' emerged. As their work travelled across national boundaries, their actors became recognised too. Brigitte Bardot, Monica Vitti, Jean-Paul Belmondo and Marcello Mastroianni were feted internationally.

Harder for European stars to gain a foothold in the US
Today, though, it is arguably harder than ever for European actors appearing in local movies to break out beyond their own borders, or to find a foothold in the US. Barre suggests that in the 1950s, 1960s and 1970s, when the auteur system was at its peak, European stars enjoyed a prominence internationally that has now dissipated.

'There were many Europeans in America and America itself was a much more Euro-centric place than it is now. Those stars of Europe and those films of Europe that came to sit in New York and other key cities for months are no longer so easily visible.'

The move towards a reliance on stars - and the reliance on them to publicise movies - has also created a gulf. As Cameron Diaz once quipped: 'I do the films for free. They pay me to do the publicity.'

A key question is how effective European actors are at playing the junket/publicity game. 'They can't say, 'I'll take a year off so I can tour with my film.' They really can't,' says Claudia Landsberger, president of European Film Promotion. 'Most of the time, they will have obligations with TV or theatre.'

Belgian actress-director Hilde Van Mieghem makes the point that an actor appearing in an underfunded European production is going to struggle to match the grooming of the Hollywood star who travels with make-up artists and hairdressers in tow. 'Star quality in Belgium doesn't mean that much,' she says. 'It has to do with money. We don't have this styling thing.'