On the side of the country lane a wooden post holds a sign indicating the route of a public footpath. Hardly a mile goes by without passing another one, maybe more. They don't stand out, so common they hardly register as we motor by. Some of us have explored where they lead, others have not.

Some follow hedgerows, ditches; others strike across open fields. Wherever they are, the landowner has a legal obligation to allow free unhindered public access. Growing crops must be cut or sprayed to keep paths clear.

Many of these paths were formed by country folk walking to church, work or market, taking the shortest route across the fields. In 1948 they were recognised and given legal status on the definitive map.

Close to villages the paths are well used. In more remote areas some are barely walked from one year to the next. Even so, they are still legal rights of way.

The celebrated fell wanderer Alfred Wainwright put together his famous Coast to Coast walk by connecting existing rights of way to form a continuous route from the Atlantic to the North Sea, passing through three National Parks.

Almost a kind of accident of history, the footpath network is now a National Treasure.