Ever wondered what they wore under their togas? Want to see a ballista pierce armour at 600 yards? Adrian Mourby joins one of English Heritage's summer events and steps back in time 2,000 years

Many, many years ago, my parents took me to Wroxeter in a vain attempt to bring Roman Britain alive in a schoolboy's imagination. We stood in our plastic macs looking at a single wall set in the middle of a wet Shropshire field. Then we went in search of a Lyons tea house.

How things have changed. The bath-house wall is still there but today Wroxeter is alive with centurions and auxiliaries marching to and fro. The 14th Vexillatio Legion (otherwise known as the Roman Military Research Society from Coventry) clinks past with big blue scutums (shields to you and me) and Paul from Roman Tours of Chester is demonstrating what the Romans wore under their togas. There are even two men practising to be gladiators.

John is immediately attracted to the swords. His eyes light up in a rather worrying fashion. Keen to inculcate any enthusiasm for the National Curriculum in my 15-year-old, I do what I can to persuade Paul to let us handle his gladius. This is the classic short-handled sword we saw Russell Crowe wielding to such effect as Maximus in Gladiator.

It's reassuringly heavy. Paul decides I should try the full legionary experience, not just the sword and armour but the marching pack - spears, bedding, wine bottles, the lot. "And you can bend in it too," says Paul, insisting we give it a try. I can see there is no doubt in his eyes that the Romans were an amazing bunch.

However, John has already moved on to a fully working ballista, something between a giant crossbow and a machine gun. It used to fire metal-tipped bolts behind enemy lines, one every 15 seconds.

It could pierce armour at 600 yards. "What happened to the bolts after a battle?" John asks hungrily. "They were expensive to make," says the Batavian auxiliary in charge, whose name is Ken, "so legionaries would go across the battlefield and pull them out of the corpses."

"Can we see it fire?" John asks. This is his kind of history. "One thirty this afternoon," says Auxiliary Ken. Unlike Maximus, English Heritage clears the field before unleashing hell.

It's all very impressive and owes a great deal to the ever so slightly obsessive men and women who spend their weekends living the Roman way of life as authentically as they can. Last night, many of these modern-day Romans camped here round the Wroxeter ruins just so they could get an early start. One of them, who gives his name only as Theodorus, is striding round with a large circular Roman military bugle (known as a cornu), about which he is singularly knowledgeable. He can also play Glenn Miller when no one's looking.

It's beginning to drizzle, which is something that the Romans always complained about in Britannium, but the enthusiasm of the organisers is undiminished. "Ladies and gentlemen, there will now be a demonstration of charioteering," announces an organiser through a decidedly modern PA system and little Theodorus backs this up by blasting out with some suitably bellicose notes.

We all crowd over to the field, under which the rest of Wroxeter lies these days, and Tony, a film stunt man, enters grappling with four huge black horses that look in danger of tearing apart his very small chariot, made of bent wood and leather

"This was the traditional racing chariot," says the voice on the PA. "The ones with sides you see in Ben Hur were only used for ceremonial processions."

Tony tears up the field at 15mph, balancing carefully and using his body weight to keep his feet on the chariot, rather like a skateboarder.

He controls the horses via linked reins that culminate in two, large leather handles - he has nothing to hold on to whatsoever. It's impressive to see the four great beasts carrying out the will of a man on such a flimsy pair of wheels - and evidently in Circus Maximus they did it at twice that speed.

"Charioteers were stars in Rome," says the PA. "But very few lived over the age of 30. Most died on the racetrack."

John nods enthusiastically, imagining huge, gory pile-ups at the Circus's first set of metae (turning posts). To his disappointment, Tony leaves the field in one piece but it's been impressive.

"Well, shall we look at the falcons?" I ask. "Or there are some mosaics in the museum and there'll be a cavalry display later..." But John's only interest is in buying a sword. He negotiates an advance on his birthday money for a great, heavy blade that's available from the gift shop, and I have a feeling his mother is not going to be happy about this.

As we drive home, I can't help feeling that my son has taken away only the more sensational aspects of Wroxeter's Roman Festival. But then at his age all I got was wet feet from standing looking at a wall.

English Heritage (0870 333 1183; english-heritage.org. uk/romanfestivals) has organised Roman festivals at Scarborough Castle, North Yorkshire, on 5 and 6 August, and Corbridge Roman Town, Northumberland, on 27 and 28 August. Prices vary