THIS week's Diary comes from Appleby in Westmorland, where I attended a small conference of crime writers who work and live in the North of England.

Although I have passed through Appleby on occasions, I have never had time to explore the town and its environs.

Arguably the most historic of the former Westmorland's county towns, it is quietly located in the valley of the River Eden, although the barren fells which separate it from the upper reaches of Teesdale are nearby.

As the crow flies, for example, High Force is a mere 12 miles or so away, albeit with the mass of Mickle Fell midway between. Even with those high fells towering nearby, the countryside around Appleby is surprisingly lush, with the Lakeland hills only a short distance away.

Although it is a very small town, it has always been regarded as important. Indeed, it was the county town of the former Westmorland, probably the smallest place in England to be a county town, and it was also the smallest which boasted an assize court, while its Corporation was one of the oldest.

The Romans, Saxons and Normans have all added their mark to this place and it has played a remarkable part in the history of England. Its Tudor Moot Hall still exists in the town centre and now houses the tourist information centre, while a magnificent castle continues to stand guard above the community.

When Westmorland was merged with Cumberland in 1974 to form the new county of Cumbria, Appleby fought to retain its previous status and the official title of the town is now Appleby in Westmorland, a permanent reminder of its former role.

Its very early history is rather shadowy, but it was granted its town charter in 1174, while the keep of the castle is known to have been standing in 1100.

A 13th century tower and the Great Hall survive, but the rest of the castle was destroyed by Oliver Cromwell. It was restored by the remarkable Lady Anne Clifford, an amazing woman who was determined to restore all her family's former houses and castles, both in that area and the Yorkshire Dales. Her family had castles in Appleby, Skipton, Brougham, Brough and Pendragon, plus the famous Barden Tower in Wharfedale, not far from Bolton Abbey.

There is no doubt she infuriated Cromwell, who regarded her as a threat to his Commonwealth, and in fact he once told her that he would knock all her castles and homes "down about her ears." She ignored him and continued her work, also restoring churches in the district.

When we arrived, the castle was closed to the public due to some dispute between the current owner and English Heritage - but it was worth the trip if only to read the notices on the main gate! I won't repeat the wording here because it is too long, but, in a most distinctive manner, it highlights the concerns and frustrations of the present owner.

Lady Anne Clifford was a very generous person, helping to educate young people and also caring for the aged. For example, part of each of her many homes was a school for the young which she visited regularly, but she also built almshouses. There is a fine example in the centre of Appleby where the elderly continue to occupy lovely cottages set around a cobbled courtyard. The public are invited to pop in for a quick look, but they are asked to respect the privacy of the current residents.

Appleby is also famous for the annual horse fair, which is held on the second Tuesday and Wednesday of June. It had finished just before we arrived and we passed several horse-drawn caravans on the roads heading away from Appleby.

The fair dates to 1685 when James II granted the right for it to be held here. It is the oldest and most important gathering of travellers in England. When they arrive, they assemble on Fair Hill to celebrate their history, music and folklore and to trade in their livestock with lots of bartering, the horses being washed in the River Eden close to the town centre. It sounds romantic, but it is not - just ask any local resident!

One surprisingly handsome structure is the police station. It occupies the same building that was erected in 1771 as the Westmoreland County Gaol and is thought to be the oldest continuously occupied law-enforcement facility in this country. The original building was enlarged during the 18th and 19th centuries, and incorporated debtors' and felons' cells, facilities for condemned prisoners prior to their execution on nearby Gallows Hill, a treadwheel and the world's first panoptikon, a quarter-circle of cells which could be viewed simultaneously by a single warder from one location.

The police station was recently featured in a Channel 4 TV programme when the main car park was excavated by archaeologists - that was the site of the original cells and treadwheel house. Local police officers are trying to increase public interest in the police station, hoping it will become more customer-friendly.

As with any town or village, the churches are of interest. St Lawrence's has a tower which is part Norman and part 15th century with a 600-year-old arch. There is also a medieval porch with a 17th century roof. It is amazing that all this has survived because the church was twice burned by the Scots and re-built, with the nave surviving for more than 700 years.

It has also survived the Reformation with some indications of its Catholic past still in evidence. The oak screen is particularly beautiful, probably dating from the 15th century, and there are some fine pewter and chained books, including a bible dating from the 17th century. Of particular note is the black and white marble memorial to Lady Anne Clifford, who did so much for the district.

St Michael's church has traces of structures more than 1,000 years old, including an ancient hogback tombstone. There are medieval stone coffins, medieval bells and the tomb of Sir Richard Pearson, a sea captain born in Appleby in 1731 who lost one of the most ferocious sea battles ever fought in English waters.

He was defending a fleet of merchant ships off Flamborough Head in East Yorkshire when they were attacked by pirates. The ships managed to flee to safety in Scarborough, leaving Sir Richard alone to fight the infamous pirate, Paul Jones. Pearson lost, but afterwards was knighted for his bravery.

Two of the men who were educated in the old grammar school at Appleby were Lawrence and Augustine Washington, brothers of the famous George who became the first president of the newly independent United States of America. Lawrence was at Appleby School in 1732, the year George was born.

One memorable facet of Appleby is the friendliness of the local people. As we strolled around the town, enjoying the peace of an early Sunday morning before breakfast or walking along the riverbanks, it was surprising how many people bade us good morning or good afternoon. And, despite there being a Saturday market in the town centre, there was no sign of litter afterwards. In all, I concluded that Appleby is a very peaceful and utterly nice place.

Tomorrow is the feast day of St Mary, but no-one can be sure which St Mary is honoured. She is not the Virgin Mary, whose principal feast day is August 15, neither is she St Mary Magdalen, whose feast is on July 22. The snag is that there are many saints called Mary and consequently the origin of this feast day is obscure. But there is a Yorkshire saying which tells us that if it rains on St Mary's Day it will rain for four weeks, and it was also on this day that the famous Battle of Marston Moor was fought near York.

The days following St Mary's feast day, July 3 until August 11, are known as the dog days and are generally regarded as the hottest spell of the summer. The name arose because, at one time, it was thought that Sirius, the dog star, rose and set with the sun during this period. The Romans created the name of dog days because they thought Sirius affected dogs, but of course the star does not rise and set like the sun. Those days are nonetheless often very hot, but I like the old Yorkshire wisdom which says: "Nivver trust a July sky."