But penetrate them the Romans did and all but wiped out the Nervians. Nevertheless, the craft of hedge laying, a technique of cutting, splicing, trimming and laying a hedge that has been practised across Europe since the Bronze Age, lived on.
The hedge offered many other benefits in addition to its obvious purpose of containing livestock and marking field boundaries. It acted as a windbreak, reduced soil erosion, provided shade and shelter for animals, and food for small mammals and birds. Around 60 species of British birds feed on the berries and bugs to be found in hedgerows and dozens of "at risk" species depend on them.
Hedges had their heyday 200 years ago when the Enclosure Acts led to an estimated 200,000 miles of hedge being planted between 1750 and 1850. The countryside of south-west England, south Wales, the Midlands and northern Ireland was thick with hedges, and the craft developed regional styles and a jargon of liggans, splashers and pleachers to describe the barriers'
different parts. But the blackthorn and hawthorn hedges so typical of lowland Britain are getting thin on the ground. In 1945, there were 500,000 miles of hedgerows in the UK, twice as much as there is now. Intensive farming, especially in East Anglia, and urban sprawl are to blame. The Council for Protection of Rural England estimates that 2,000 miles of hedges are still being destroyed every year, but ancient hedgerows are now protected under the 1997 Hedgerow Regulations.
Domestic gardeners used the hedge as a decorative border, and topiarists got busy with their shears, trimming the close-growing privet and yew into new and unusual shapes and mazes. But while more and more old-fashioned countryside hedges are neglected or destroyed, one particular variety of hedge is thriving. Cypress leylandii trees grow thick and fast, offering privacy to some and darkness to others, sometimes prompting bitter disputes between neighbours. Not since the Nervians' last stand has there been such fighting over a hedge.
Hedges to visit:Levens Hall, Kendal, Cumbria. World-famous collection of topiary dating from 1694. Tel: 015395 60582; www.levenshall.co.uk.Longleat Hall, Wiltshire, world's longest hedge maze with nearly two miles of paths. Tel: 01985 844400; www.longleat.co.uk. Meikleour Hedge, on the A93 to Perth. World's biggest beech hedge - 30 metres high and 540 metres long.