The casual observer might think this is just a piece of theatre, but David has done his homework. In between asking the children about their favourite Gladiators ("Wolf? I've never heard of him") he also tells them about his day-to-day life, his diet and his "dress".
This combination of information and entertainment is what a good school trip is all about, and teachers taking children round the museum were in no doubt as to its effectiveness.
"They think they're just enjoying themselves but they're learning too, " said Veronica Romain, who was with a group of Year 4 pupils from Greenfield primary school in Northolt, Middlesex. David Pepper, from Saint Monica's Primary in Hoxton Square, regularly brings classes to the museum. "It's marvellous to have a live Roman. The children love asking him questions."
Apart from the role-playing, the museum offers hands-on history lessons where children can get to grips with real ancient artefacts, an archaeology workshop, teachers' short courses on aspects of the history curriculum at key stages 2 and 3, plus a visit planning service.
"Given all the demands on their time, teachers want to come to our museum for things that are directly relevant to the curriculum so we have to offer things that do that," explains Emma Webb, the museum's education officer.
Large museums have more resources, but bigger is not always best. Local museums may have more problems in meeting the demands of the curriculum than their national counterparts, but they will often excel in other areas, loan services, for example.
A national report on museum education found that two thirds of the 566 museums surveyed said education was an essential part of their function.
Schools account for about l0 per cent of attendances. National museums had the most comprehensive educational facilities but a disproportionate number of armed forces museums had no provision.
"We found that although the number of education posts in museums has doubled in the past 10 years, it is nowhere near the level of demand," says David Anderson, head of education at the Victoria and Albert Museum and co-ordinator of the report. "Local management of schools has meant some education services have come under financial pressure and in some places LEAs have withdrawn staff. One of the most compelling arguments for museum education is that museums have a central role to play in the education of society and schools are one of the crucial factors in that."
However, Roy Hughes, head of St Paul's School in Salford and chair of the Historical Association's primary group, says that what schools want from a museum and what museums offer schools rarely coincide. "Museum education needs to deliver the national curriculum. Museums should concentrate on the significant and not on the trivial. Part of the problem is that a trip to the museum is thought of as just a day out. It should be more than that."
Far from laying the blame at the door of museums, Roy Hughes thinks that teachers could do a lot more in the way of preparation and planning, making sure children know what they are going to see and what they will be learning about. "Children need to have prior knowledge, they need to be given an appropriate historical vocabulary and an awareness of the period they are studying beforehand. They need to know just what the visit is supposed to be about and what to expect. That's not all the museum educator's job."
He suggests teachers should set tasks which develop pupils' historical skills such as observation, imagination and questioning. But they should be careful not to try to cover too much. Large museums boast huge numbers of exhibits and better materials for school visits but may overwhelm small children.
Unfocused foot-slogging round big museums can leave children having seen a lot but learned very little. A well planned visit to a small two room museum may provide just as much opportunity for learning. "It doesn't matter what size the museum is. Above all, a museum visit should be about making children understand."