Walking: Following a route set in stone: Roy Woodcock begins the first leg of a two-part geological walk across southern England

THIS LONG cross-country walk grew out of a geological idea. I wondered if it would be possible to walk from coast to coast across southern England on calcareous rocks (chalk and limestone) all the way. The answer turned out to be not quite, because of a few stubborn miles in Somerset. As I planned the route, starting at Brean Down just south of Weston-super-Mare, and ending 305 miles later at Dover, I realised that it could pass a many places of historical interest.

The prominent ridge of Brean Down sticks out like a finger into the Bristol Channel, and it was from here that Marconi sent his first message across the water in 1896. It was also from here that my cross-country walk began, at the site of a fort built in the 1860s, and a Second World War gun emplacement, both fortifications built to counter possible attacks from Europe.

From this most westerly point, I walked east along Brean Down, passing evidence of Bronze Age, Iron Age and Roman settlements on this carboniferous limestone hill, which is an extension of the Mendips. Beyond the river Axe and the village of Uphill, I followed the route of the West Mendip Way along the top of the Mendips, often exposed and windswept but giving magnificent views across the Somerset Levels.

I then traced the Avon-Somerset boundary for a few miles, passing the popular Cheddar Gorge - the Grand Canyon of Britain - the far- quieter gorge at Ebbor and the tourist honeypot of Wookey, before reaching the cathedral city of Wells. Four other fine cathedrals and 50 churches will be passed on the way to Dover.

To the east of Wells there is more carboniferous limestone, although the land is lower and undulating towards Shepton Mallet. Beyond Shepton, Jurassic limestones as well as some sands and clays are crossed before reaching Stourhead, passing through Chesterblade, Batcombe, Bruton and South Brewham, all of which have small churches constructed of the local stone.

This coast-to-coast walk does not cross any national parks, but does visit nature reserves, areas of outstanding natural beauty, green belt, and other protected areas. Brean Down, Ebbor Gorge and Stourhead are in the hands of the National Trust, which is not only an excellent manager and conservator of fine houses, but also of these areas of the countryside.

Just before reaching Stourhead, I crossed into Wiltshire, passing Alfred's Tower, perched on the top of the sandstone ridge. It affords commanding views over the surrounding countryside, and was built as a memorial to Alfred the Great, who erected his standard here while fighting the Danes in 879AD.

The architect Henry Flitcroft, and Henry Hoare I, a London banker and son of the Lord Mayor, built Stourhead House in the 1720s. Henry Hoare II created the landscaped garden, and succeeding generations have added to both the garden and the house. The garden was an attempt to design with the eye of an artist, rather than with the precision of a surveyor, and this was the method which became popular and fashionable with Capability Brown and other landscape gardeners later in the 18th century.

From the steps of Stourhead House can be seen Whitesheet Hill, the beginning of the chalklands which extend all the way to Dover. Most of the chalk grassland has long since disappeared to make way for cereal production, but in the last two or three years other crops have been grown there, as well as seeing a return to grass for cattle and sheep.

This hill was used in Neolithic times for sheep and cattle pasture, there are Bronze Age burial mounds from 2000BC and an Iron Age camp from about 500BC. The track leading to the top of the hill is called Long Lane, and was used to carry Cornish tin in the Bronze Age, subsequently becoming a turnpike in the 18th century.

When replaced by the new road along the foot of the hills, it continued to be used as a drove road for the huge flocks of sheep and cattle being driven to the fairs at Yarnbury Castle, east of Wylye. An old milestone dated 1750 can be seen on the approach up to Whitesheet Hill.

Travellers have been moving around England for thousands of years, and many signs of their routes were encountered on this cross- country walk. This route over Whitesheet was probably part of an old route called Harrow Way or Hard Way, which went from Devon to Kent via Salisbury. Roman routes were followed from Salisbury to Winchester, and the Pilgrim Way can be found along the North Downs. The route eastwards undulates over the chalk, and passes through the attractive stone villages of Kingston Deverill, Hindon, Fonthill Bishop, Steeple Langford, Berwick St James and then on to Stonehenge.

An important piece of history can be found here, even if no one is quite sure of what it all means. The first Stonehenge was a Neolithic earthwork built 5,000 years ago, and about 1,000 years later it was rebuilt using bluestones from Pembrokeshire, over 100 miles away.

The third phase came soon after, using the larger sandstone rocks or sarsens, from Marlborough Downs. What we see today in this unique monument are the ruins of the prehistoric temple which was in use 3,500 years ago.

Turning my back on this pile of stones, I headed southwards down the Avon valley to Salisbury, pausing at Old Sarum on the way. First inhabited in the Iron Age, it then became a major Roman fortress. The Saxons built a town here, and a cathedral was constructed within the earthworks.

In the 13th century, as the disputes with the military occupants of the castle became more irritating, the bishop moved two miles southwards to New Sarum - now Salisbury - and built his cathedral there. The foundation stones of the new cathedral were laid in 1220, and the 404ft spire can be seen from miles around. Made famous in a painting by Constable, it is one of the most dominant landmarks on the entire walk.

Roy Woodcock completes his coast-to- coast journey next week

(Photograph omitted)