The assumption perpetuated in many history books is that Celt roundhouses had a hole in the roof to allow smoke to escape. But the archaeologists and scientists at Butser Ancient Farm in Petersfield, Hampshire, have disproved this theory. They painstakingly reconstructed a magnificent roundhouse complete with hole and watched it burn as sparks caught on the thatch.

They take a long-term view at Butser, a working farm and open-air laboratory founded in 1972 to carry out research over many years into prehistoric and Roman agricultural and building technologies. Using evidence from excavations, the archaeologists have hand-built a full-scale Roman villa with hypocaust (underfloor heating) alongside existing reconstructions of three Iron Age roundhouses.

The villa project was funded by and filmed for the Discovery Channel’s recent Rebuilding the Past series. The flint and mortar walls were finished using authentic wet or dry plastering techniques. It has a mosaic floor copied from an original, and the frescoes feature the “Romanised” faces of project workers. Experiments are being conducted on heating, how cooking was done, and much more.

An education programme covering the Anglo-Saxons, Vikings and Romans focuses particularly on what it was like adapting to the way of life the Romans introduced.

On my visit , Year 8 girls from Sutton high school in Surrey, studying the Cambridge Latin course, are gathered around the fire in the chief roundhouse being addressed by education officer Maureen Page. “Roman invaders were soldiers and had no time for farming”, she says. “They came to enslave people and plunder metals to make tools and weapons. Life changed and became much like your parents’ lives today. Everyone had a job but would have hired help for other chores and paid taxes to the Empire”.

The roundhouse, she explains, is based on a Salisbury Plain excavation.

From the post-holes, which are all that remained, archaeologists knew the size, but not its height or what the roof was made of. “We built this hut three times until we got it right, but can only guess what it contained as furniture and floor coverings would have rotted”, she says.

The girls split into rotating groups to compare the differences between the Roman and Celtic structures, build a Roman flint and lime mortar wall, and made a spiral torc (bracelet) out of copper wire to take home. Other activities include spinning with a drop spindle, weaving, surveying, making a clay plaque, and putting a model hypocaust together.

Meanwhile, Year 4 children from Cothill House preparatory school in Abingdon, are building a wattle and daub wall by weaving hazel rods into a lattice and coating it with a mixture of earth, straw and grass.

They learn about ancient breeds of sheep, which lost their fleece naturally, and excavate finds in the archaeological pit, including a piece from a ploughshare and a Roman roof tile. “We like the way it’s done here, with an introductory talk and hands-on stuff; it’s much better than boring worksheets”, says one Sutton student.

Sutton’s head of classics, Lesley Griffiths, pronounces it an “excellent day, which reinforces the Pompeii topic studied this year and prepares them for the next unit on Roman Britain - on the Romans coming into the Celtic situation”.

Butser Ancient Farm. Tel: 023 9259 8838; www.butser.org.uk. Admission costs pound;5.25 per child (minimum group admission pound;100). Free teachers’

planning visits are available