A ROMAN siege engine called an onager – potentially capable of firing a 4.5kg weight more than 360m – will get its first public demonstration at the Secrets of the Heath event on September 5 and 6, 11am-5pm each day.

Petersfield Heath will be filled with the sights and sounds of 3,000 years of history, including mediaeval warriors, a highwaywoman, Saxons and English civil war re-enactors.

The onager, named after a type of wild horse, would have been used towards the end of the Roman Empire to destroy town and city walls by firing large rounded boulders. But this one, measuring 1.8m in height, will be loaded with old vegetables and fired every hour over the two days.

Ryan Watts is an experimental archaeologist at Butser Ancient Farm and is the creative mind behind the contraption. He said: “This is the onager’s first public outing.

There has not been much work done on this type of machine before – especially one this size, which we think is the biggest in the country. According to our calculations, we think it could throw a 10lb object 400 yards – although this might be underestimating the size of our machine.”

Another new activity this year will be an archaeological roadshow where people can bring in their own finds, from flints to Roman coins. Experts from Petersfield Museum will identify them and will also be conducting a live archaeological dig of an ancient sewer over the weekend of the event.

On Saturday night there will be a stargazing party and bat walk.

Visit www.southdowns. gov.uk/enjoy/events/secrets-of-the-heath-2015/ for more information.