For sheer imaginative brio, "Pan's Labyrinth" is one of the films of the year. But the dark fable was a labour of love for director Guillermo del Toro, who says that violence in his native Mexico is key to his extraordinary vision. 'A maze is a place where you get lost," he explains. "But a labyrinth is essentially a place of transit, an ethical, moral transit to one inevitable centre. You think of the transit of Spanish society from the 1940s to the incredible explosion of the post-Franco period. The 1980s in Spain were like the 1960s in the rest of the world." Mark Kermode reports.