THE Mercian King Offa (AD757-596) would be in a spin that walkers today are running rings around his ancient line of demarcation and defence.

The Offa's Dyke Trail was one of the first National Trails, and is still one of the most popular, attracting walkers from both sides of the English/Welsh border and up and down the length of the trail which runs from Prestatyn down to Chepstow. Established in 1971, the trail passes through some of the best hill walking areas in the country. It is continually evolving as diversions are established to improve the quality and safety of walking, and also to stop increasingly severe erosion, not surprising after almost 3,000 years.

'Offa's Dyke Circular Walks: southern section' is the first in an excellent two-part series (the northern section following next year), enabling walkers to sample the delights of the trail using 25 circular routes, matched to their own abilities. The walks are situated between Knighton (Powys) and Chepstow, and range from five to 13 miles (three to seven hours). Detailed but concise instructions include height gain, local facilities and summaries of terrain and ground conditions. Sketch maps are to scale, a boon in this demanding terrain. Suggested starting points give the most energetic walking in the first few miles. With Volume 2, this will be the only guide detailing energetic walks using most of Offa's Dyke Trail.

Ian Coulthard lives on the Wirral and is a keen and experienced walker and writer. He has previously produced 'packs' of maps and information for the Cotswolds and the North Yorkshire Moors, which have proved to be very popular. Ian has written this book particularly for those who share his passion for energetic hill walking, as he comments: "Frustration of retracing ones steps is alleviated in these books. The circular walks pass through some of the most beautiful scenery, national parkland, areas of outstanding natural beauty and historic border towns. With plenty of information to help walkers, I hope they will enjoy exploring and appreciate the borderland as much as I do."

These books will make an invaluable addition to any serious walker's library.

'Offa's Dyke Circular Walks: southern section' is published by Sigma Leisure, ISBN 1 85058 725 6, price £7.95, and is available from all bookshops.