The French performance art group Ilotopie lent a whole new meaning to the phrase 'painting the town red' at the South Bank open-air festival last year, when they mingled with the crowd clad in nothing but virulent coats of paint (right). Unruffled by the somewhat startled response of passers-by, they queued for the Hayward gallery, wandered into the Magritte exhibition and round the coffee bar and eventually drifted off over Hungerford Bridge to make their presence felt in Trafalgar Square.

This year they will be safely under lock and key. In La Mousse en Cage, appearing as part of The Great Outdoors on the South Bank, the artists begin the show imprisoned in cages. This time they won't be wearing paint, but coloured foam will start to ooze from their costumes, frothing and bubbling as it hits the air, and gradually solidifying to incarcerate them further. When they are completely immobilised in solid froth, they hope their audience will help to release them. Otherwise it could be a difficult journey home.

The company - which brings together sculptors, painters and decorative artists - has worked together for the last 10 years from an island off southern France and specialises in installations in public places, large and small (though they once took over an entire block of flats, in Hong Kong they confined their attentions to a bus stop). Size, however, prevented them from bringing their intended show about the Channel Tunnel to London this year: the piece demands a space 130m long - too ambitious for the South Bank river walkway. Rachel Clare, artistic director of The Great Outdoors, still hopes to bring the show over next summer, and, as she points out 'Maybe we'll still be in time for the opening of the tunnel'.

Ilotopie performs 'La Mousse en Cage' on the South Bank

in front of the Royal Festival Hall, SE1 on Sat 13 and Sun 14 Aug at 2.30pm

(Photograph omitted)