Oh country house hotels, what crimes are committed in thy name! Since the 1980s when this genre emerged to feed the upwardly mobile pretensions of the era's yuppies, there have been many cynical attempts to confect a rural, aristocratic douceur de vie for the benefit of the paying public. But simply taking some Victorian monstrosity (formerly a private mental asylum), building a golf course in the grounds, adding minibars and cable television to the bedrooms and a set of indifferent oil paintings and some suits of armour to the public rooms will not, in fact, recreate the fugitive charm of Brideshead Revisited.

To such vulgarities, a place such as Glin Castle in County Limerick is a standing reproach. Of course, it does start with several advantages. First, it remains a private residence: the home of Desmond FitzGerald, the 29th Knight of Glin, whose family has owned the land around for some 800 years. From March to November, its 15 bedrooms are at our disposal, but for the rest of the year, it is simply a family home, its beautiful, elegant rooms adorned with FitzGerald portraits and the furniture and objets d'art they have assembled over the years. (The Knight is a distinguished art historian and president of the Irish Georgian Society and Glin is decorated throughout with pitch-perfect taste.)

Second, the building is a small masterpiece of Irish domestic architecture, begun in the 17th century, but mostly created towards the end of the 18th, when the family felt confident and wealthy. It was their misfortune and our gain that their finances failed around 1800: this meant that Glin was spared the 19th-century "improvements" that disfigure so many Georgian country houses, though it was charmingly Gothicised with turrets and battlements like a toy castle. (The money ran out so suddenly that some bedrooms on the third floor were prepared for plastering, but then abandoned and completed only in 1999.)

And third, and most importantly, the Knight and Madam FitzGerald - and their peerless manager Bob Duff - create such a relaxed and friendly atmosphere that it is easy to feel that you actually are a guest in a country house. This flattering impression is aided by the complete absence of the pompousness and formality of a posh hotel. No reception desk, no concierge, no uniforms. If you need anything - a drink, a sandwich, a booking on the golf course at Ballybunion - just go and find Bob who will fix it for you. The food in the dining-room is elegant and unpretentious: the meat is locally sourced, the salmon from the broad Shannon which the castle faces, the organic fruit and vegetables from the walled garden in the graceful landscaped grounds.

Amid such ease and comfort there is just a tinge of pleasant melancholy that one is enjoying one of the last examples of the once great Anglo-Irish Ascendancy culture. Glin Castle is the perfect place to read the stories of Somerville and Ross and the novels of Elizabeth Bowen and Molly Keane: to understand the world they are describing and which has now almost vanished.

Glin Castle, County Limerick, Ireland, 00 353 068 34173, www.glincastle.com. For further information email knight@iol.ie, double room, b&b, from €280 (£190). Dinner from €48 (£32)