Major's view of the country: Dead sheep, live rats - and now a shire-horse plays a starring role in art. Naseem Khan sees Housewatch at work

It's a tense moment - the time when a small performance group meets its newest recruit for the first time.

The proposed new member - introduced simply as 'Major' - stands patiently while the three - Lulu Quinn, Tony Sinden and Stanford Steele - circle him critically. There can be no doubt that he is impressive - massive, muscular. He does not speak, but then he hardly needs to.

Major gazes into the middle distance calmly, unfazed by the scrutiny. Then he proceeds to urinate on the floor. The three regard the long, steady stream thoughtfully. 'We'll need buckets,' says one, 'And sand.'

Major the one-ton shire- horse offered the three artists who comprise Housewatch everything they wanted. Having passed the audition held in a country barn, he is now part of of a large-scale installation in the Royal Festival Hall, London from today. Called Fallow Field it is an exploration of the countryside, via video, smells, sound, an evocatively built environment and, of course, a real horse.

Major's part may simply be walk-on (and he will not be present for the whole run), but it is important. He will act as a corrective to romantic expectations of the countryside. 'It's the sheer presence and scale of the horse to start with . . .' says Lulu Quinn. 'But the thing that is going to be really important is the inconvenience - what are we going to do if it shits and pisses?' Major is there to provide an edge of nervousness, of a force that is potentially not controlled.

The elements of dislocation and unease are not uncommon in Housewatch events. Created by a loose collective of multi-media artists, they have, over 10 years of activity, eschewed the gallery. Instead they can be encountered in underpasses and the street, in houses and cars.

Kyoto, for instance, was host recently to their Paper House, a large cube made from paper and erected in a city square. By day it looked chaste and neutral, but when evening fell, video images projected from inside the cube transformed it. Water ran down its surfaces; machinery encircled it. The spectacle held crowds spellbound.

The installation in the South Bank's Festival Hall is similarly large-scale. It is based on the idea of a barn. It is made out of black agricultural netting with the intention of being shadowy and dim - the antithesis of the gallery's cool white space. Inside will be feeder-troughs filled with cattle fodder, and long rows of 16 video monitor screens. These will be playing three 20-minute sequences, one by each artist, culled from many hours of footage shot by each one during the agricultural year.

To prepare Fallow Field, the artists took to the fields with video cameras and started to record what they found. Video footage piled up asthe seasons changed; they examined and re-examined the images they'd brought back - mud, mechanical processes, footprints, crops and produce.

Each artist gradually began to develop a separate path. Steele's led him towards machinery and the character of ploughing. Quinn rode on combine harvesters and filmed the activity as if it had been shot by the machine itself. She was struck by the quality of rural noise, and so were they all. Bouts of action and stillness, clamour and silence, alternated incessantly.

'There isn't any permanence,' explains Sinden. 'Once you start to look, you realise everything is changing all the time. You never know what's going to happen, from one moment to the next.'

Reflection binds the exercise together. The dim space of the barn with the sounds of the country and the amplified breathing of the horse provide a space in which to reflect. The artists themselves are carefully non-committal. Fallow Field is not a documentary about farming, nor a polemic about the mechanisation of agriculture nor a diary of the farming year. 'It's setting out to stimulate and evoke people's interest,' says Steele. 'It's as simple as that.'

Royal Festival Hall Galleries (071-928-8800). 10am to 10pm until 11 Sept. Free