Rumours review - close encounters for Cate Blanchett and the magnificent G7

Cate Blanchett has supplied the strangest moment of this year's Cannes film festival; for Brits of a certain age, anyway. Her character reverently invokes the name of the late Roy Jenkins, Labour grandee and former chancellor of both the exchequer and Oxford University. Blanchett plays a fictional German chancellor called Hilda Ortmann who mentions Jenkins as the first president of the European Commission allowed to attend a G7 summit (which, as political trivia connoisseurs would say, is "one for the heads".) Perhaps in her next film Blanchett can do a big speech about Peter Shore.

Rumours is an amusing drawing-room absurdist comedy, co-written and directed by Canadian film-maker Guy Maddin with his longtime collaborators, the brothers Evan and Galen Johnson. The title is inspired by the 1977 Fleetwood Mac album, because of the emotional crises that are said to have accompanied its recording. The setting is a forest in the German town of Dankerode in Saxony where a fictional G7 summit is taking place. Seven government heads have gathered to discuss an unspecified (but apparently ecological) crisis and to draft a lengthy and fantastically unhelpful communique which, as Hilda murmurs to her French counterpart, President Sylvain Broulez (Denis Ménochet), should be worded vaguely enough so they are not committed to any specific action. The US president Edison Wolcott is ageing and somnolent; he is played by Charles Dance, confusingly with his own English voice, and the script has a joke about Dance being apparently unwilling (but surely not unable) to do an American accent. British PM Cardosa Dewindt (Nikki Amuka-Bird) is stressed because she had an affair at the last G7 summit with troubled Canadian premier and ladies' man Maxime Laplace (Roy Dupuis), who also carries a torch for European Commission secretary-general Celestine Sproul (Alicia Vikander) and has a moment with Hilda. Rolando Ravello plays the nervy Italian PM Antonio Lamorte and Takehiro Hira plays Tatsuro Iwesaki, the modest, shy Japanese premier.

Their lakeside G7 dinner is thrown into crisis when they realise that their phones don't work; the chateau HQ and probably the whole town has been abandoned and they are now utterly alone - except for the 2,000-year-old humans discovered embalmed in the Dankerode clay which have now come to life, stumbling around the place and frantically masturbating so that the resulting tsunami of seed will both extinguish the catastrophic fires and engender an enlightened new people. This is a very strange film, like a mixture of George A Romero with a crimeless, detectiveless Agatha Christie, and maybe TS Eliot's The Cocktail Party. Blanchett shows herself to be actually pretty good at playing comedy, leading the company in some very amusing set pieces. At the dinner she announces to her six guests that the theme of this year's summit is "regret", and says that they should now go around the table and say what they most regret. Tatsuro rather charmingly says that he regrets not learning to ride a horse; Sylvain begins to choke with tears as he says that he regrets not ever really understanding his father. Clearly, the rest of the group are feeling the pressure to say something powerful or moving. Next up is the Italian president who blurts out that he regrets going to a fancy dress party as Mussolini.

Rumours is weird and confusing, with strange forest encounters and apocalyptic episodes. There is a genuinely bizarre gag about an AI chatbot programme designed to trap paedophiles. Hilda discovers the goodie bags that each G7 member was supposed to get, and each contains a cyanide tablet - this provision is now normal, she explains. A droll account of the world's whimpering end.