This is one of our best Iron Age monuments

The Trundle. It is the pinnacle of the Goodwood Estate, and right next to the horse-racing grandstands so everybody knows where it is.

But what is it? Well, it is one of our best Iron Age monuments, built 2,250 years ago. It was a small city for only 200 years, a walled defence against other tribes. The women who lived there wore adjustable finger rings made of bronze.

They made their own cooking pots of local clay and heated the water by placing red hot flints inside. The men sometimes shaved their beards.

The forts had underground grain stores and water catchments so could be used as refuges during attack from outside. Similar forts were erected at Cissbury, Torberry, Old Winchester Hill and St Catherine's Hill while the Caburn seems to have belonged to a slightly different tribe.

They were invaded by the Trundlers, who looted luxury goods like those adjustable rings and upmarket brooches.

But the main threat to our ancestors from the late Stone Age was from foreign tribes on the continent, especially Dutch, German, and French as we now call these countries.

By the time the Romans invaded the Trundlers had moved off this draughty hilltop with their horses, cattle, pigs, sheep and dogs on to the plain near Chichester: half a century before Christ was born.

The idea for such monumental forts had originated in the Near East. Troy and the Acropolis in Athens were examples and the idea spread among the Barbarians northwards until the Germans developed these as earth and stone walls bonded with a huge timber frame. The blueprints were brought to Sussex by the Halstatt invaders.

The defensive walls were fine while they lasted, with vertical walls. Once the timber rotted they became very expensive to repair.

The main gate at the east side was rebuilt three times with new upright tree trunks. The final gateway, never completed, had a barbican or overhead sentry box.

Today the banks and ditches grow some of the best chalk grassland in the county.

Large numbers of pyramid orchids bloom in June, with earlier spotted and bee orchids, and early purples in May.

Blue butterflies live off the masses of bird'sfoot trefoil, meadow browns off the long grass in the centre of the Trundle.

The circular banks provide a lovely short walk when you can view the English Channel, West Dean arboretum, the finest yew forest in Europe at Kingley Vale (top of my picture) and the hills of Surrey to the north.