Offa was King of Mercia between 757 and 796. His kingdom covered the area of England that is today known as the Midlands, and was the largest and most powerful in Britain at the time.
Offa minted his own coinage and saw himself as the equal of Charlemagne. He was also responsible for the great Offa's Dyke - a great earth bank marking the ancient border between England and Wales. It runs from the North Wales coast to near Chepstow on the River Wye in the south.
His dyke was never fortified and it was probably built as a barrier, a way of marking the frontier and protecting his kingdom. Legend has it that the English cut off the ears of every Welshman found to the east of the dyke, and the Welsh hanged every Englishman found to the west of it.
The dyke is an earth bank, with a ditch on the Welsh side, and a raised bank up to 20ft high on the English side. It was built by hand, with local labour expected to dig 4ft 11Z2in (125cm) of earthwork before being allowed to return back to their farms.
At 176 miles, it is 8 miles longer than Hadrian's Wall and considerably more accessible. Backpackers walk it in around 12 days, but school groups can use it for short trips, for Duke of Edinburgh Award expeditions or as part of an area study.
The modern dyke is the route of a well-marked long-distance footpath - hence the number of backpackers - but school groups will want to concentrate on those areas where the dyke is best preserved. Surviving sections can be seen in the Wye valley and on the ShropshirePowys border.
Schools can use the dyke in combination with other venues, or as the basis for the "walk with a purpose", which is the foundation of the Duke of Edinburgh's Award scheme.
Either way, the starting point should be the Offa's Dyke centre in Knighton. The centre is run by the Offa's Dyke Association. It is staffed full time and offers maps, circular walks, information and guidance. The centre building sits on the dyke's route, with one of the best preserved and most spectacular "switchback" sections running north from Knighton to Welshpool.
The centre has a room for school bookings and children can safely let off steam in the grounds. The overhanging roof offers a venue for lunch.
* The Offa's Dyke Centre
Knighton, Powys LD7 1EN Tel: 01547 528753 E-mail:firstname.lastname@example.org www.offasdyke.demon.co.uk
The Offa's Dyke Centre can suggest campsites for Duke of Edinburgh groups along the dyke's route. For larger groups, there are several YHA youth hostels
Llangollen (north section, 31 beds ) Tel: 0870 7705932
Clun (mid section, 24 beds) Tel: 01588 640582
St Briavels Lydney (south, 70 beds) Tel: 0870 7706040