Outdoors: South Downs National Park

And, of course, you know there are 15 National Parks; ten in England, three in Wales and two in Scotland, and they cover such diverse landscapes as Dartmoor, the Peak District, the Lake District, the Brecon Beacons and the Norfolk and Suffolk Broads, while in Scotland they comprise the Cairngorms and Loch Lomond and the Trossachs.

Described as "Britain's breathing spaces", they resulted from the early 20th century movement for rights of public access, but it was only the mass trespass of Kinder Scout in 1932 that spurred the authorities into action. Well, action of a kind, for it was 1951 before the first National Parks were created "for the benefit of the nation".

The last in the list was the New Forest in 2005 and, as of 1 April, we now have the South Downs National Park, and a very big deal indeed for Hampshire and Sussex, across which the park stretches.

This newest park is the most populous of all 15, encompassing towns and villages, and extends from Winchester in the west to Eastbourne in the east. It takes in coastal areas such as the Seven Sisters and Beachy Head, measuring 170km in length and with a network of more than 3,000km of paths.

All this you may know. But have you been there? No. Let me take you by the hand and show you a small part of Sussex, one of my favourite English counties, one of the most beautiful and, for years, a well-kept secret, now about to be much more widely known.

We based our stay in Midhurst, West Sussex, where the South Downs National Park Centre is located. An obviously prosperous town from early Tudor times, it is home to Cowdray Park and the ruins of Cowdray House, home of the Montague family.

They served both Henry VIII and later Elizabeth I, although they were prominent Catholics, and were also involved in the Gunpowder Plot. As promised by the Cowdray curse, the family line came to end by fire and water, with the house destroyed by fire in 1793 and the heirs to the dynasty subsequently drowned in a boating accident.

So it is the ruins of Cowdray House that you see as you approach the town. The narrow lanes and square also contain many ancient buildings, notably the old grammar school, founded in 1672 and numbering among its pupils HG Wells. So pretty is the town that it has been the backdrop to many film and TV productions, including Foyle's War. I'm sure you get the picture, and if you don't, a stay at the Spread Eagle Hotel and Health Spa will place you firmly in the town's history.

Heavily beamed, with great open fires, and without a single straight wall to be found in the place, it dates from 1430, with a "newer" 16th-century wing. But if you push the boat out and book the Queen's Suite, you are not only in the 15th century, but also sleeping in the room where Queen Elizabeth I stayed in 1591.

There is a four-poster, a separate wig closet, and the floor is spectacularly uneven – sloping up to the bed, and with so many dips and contours that walking across it in high heels gives a drunken sailor effect – but the bathroom, mercifully, is right up to date. There is even a thickly padded and beautifully upholstered section of beam above the toilet, to ensure taller people don't knock themselves out when they are rising or backing away from said toilet.

But enough of high heels, beams and towns; we donned our walking boots and set out to explore the South Downs. The hotel delivered us right to Cocking Down, complete with maps, a rucksack containing a picnic, and instructions to telephone them when we wanted picking up again.

From the car park we walked up and into the chalk downs. This doesn't have the grandeur of the Highlands; it is softly cushioned countryside. If you threw down a heap of fat, green velvet cushions, punching folds and dips into them, putting farmhouses in some of the dips, thick woodlands in others and along some of the slopes, and scattered some wildflowers, there you have the Sussex downland scenery. There are some conifer forests, but it is mainly ancient woodland – beech and oaks – and I was told that further south, just above Chichester at Kingly Vale, there is a grove of ancient yew trees that are among the oldest living things in Britain.

In the South Downs there are six Marilyns, none of which we would encounter on our visit, for this route was considered a relatively sedate local walk, and those higher hills are further afield. But we did find ancient tumuli, woods that were allegedly home to wild deer and, in the terrain of small fields and gentle hills, we encountered cows, some sheep and glorious wild flowers.

Up and down the ridges of the well-signposted downland we went, with some closed valley views as we slithered down the slopes, some wide open vistas when we broached the hills, particularly at Beacon Hill, site of an Iron Age fort, and with views, on a clear day, to Chichester and the coast.

We didn't have a clear day. We had mist and rain instead, therefore no great view, and so descended into the pretty village of Elsted and the comfort of the Three Horseshoes pub to dry out a little, and experience more history, more beams, an open fire and a fine choice of beers and food.

Then onwards and upwards, or rather out and round the pub garden, following the contours of the land and the signs, to complete the circuit at Cocking Down, and a telephone call to take us back to the hotel, a welcome pot of hot chocolate, a swim and massage in the spa and the promise of dinner.

To anyone used to Munros and Marilyns, we didn't do well; a mere 11.5 miles and only a small section of the South Downs Way attempted. There are longer walks mapped out; there is even talk of the Spread Eagle organising a week's walking tour to take in the whole of the South Downs Way from Winchester Abbey to Eastbourne Cathedral.

But our small effort was an introduction to make us want to do more, for the beauty of this area of Sussex is seductive. To walk here is to glory in the sheer, lush prettiness of the countryside, and to celebrate that we have a new National Park "for the benefit of the nation".

Where to stay The Spread Eagle Hotel and Health Spa, Midhurst, West Sussex (01730 816911, www.hshotels.co.uk) has walking tour breaks from 220 for a midweek night in a standard room, including bed and full English breakfast, three-course dinner, use of spa and pool, picnic and walking map. Flights from Edinburgh to Gatwick with easyJet (www.easyJet.com) from 41. Gatwick airport is within an hour's drive of Midhurst.

This article was first published in The Scotland on Sunday, June 13, 2010