It was Napoleon, of course, who founded the French National Stud as we know it today. In charge of an army totally dependent on a million horses, he needed to replace a hundred thousand of them even in a good year. And the favoured horse of the French Army was the Norman Cob. 

The Cob was the ideal general-purpose horse. Manes and tails cut short for practicality, six of them could drag a field gun, while one would carry a heavy dragoon and the occasional infantry passenger. Four cobs was the ideal team for a heavy wagon; the breed is compact, muscular and immensely hardy. 

The Haras National today has 26 separate establishments, most of them still in Normandy, which is also the motherland of the present-day French general-purpose horse, the Selle Français. Normandy is amazingly rich in horse-breeders; one of its five départements, the Calvados, has 1,388 breeding establishments – four in every ten square miles.

Centred on Deauville, the Calvados breeds trotters and thoroughbreds for the most part, and is the home to 247 stallions. In the neighbouring département of Manche, however, the National Stud at Saint-Lô is home to 200 stallions of seven breeds. And from July to March it's open to visitors every day; and best of all, it's free. The kiosk at the entrance is there to sell postcards, not tickets. 

The buildings of the Haras National take up a sizable portion of the town centre of Saint-Lô. You are advised not to miss the magnificent city walls that surround the other half, especially as the Haras entirely lacks a car park. Once you have walked up the road and through the gate, however, you are in horse heaven. The vast central courtyard, three hundred yards by two hundred, is surrounded by four curved stable blocks. Set back from the gap opposite the gate is the Master's House, an eighteenth-century jewel; at opposite ends of the long central alley are the riding school and the coach house. Gravel rides run all round the court and across it in both directions, four well-kept lawns between them. 

Once inside, you are free to visit. Areas needed for work in progress will be politely roped off; but you can browse round the 50 stalls of each stable, containing the cream of French bloodstock, or visit the tack rooms, coach houses and farrier's shop.

In the stables you will find stallions of seven breeds, from ponies to Percherons, each neatly labelled with name, age, sire, dam and sire of dam. There are thoroughbreds, of course, though not in great numbers here. The French thoroughbred descends directly from the English, of course, though most have a common ancestor in Gladiateur, the first French Derby winner in 1865.

French racegoers, however, have a marked predilection for trotting races, and the second breed on show is the Trotteur Français. They descend from a cross between thoroughbreds, English hunters and Norman mares. Theirs is one of the most open stud-books, and they vary considerably in size and type.

The breed most represented at Saint-Lô, however, is even more recent in conception; the Selle Franais(French saddle-horse). The stud-book for this breed was opened in 1958, and its ingredients include the Anglo-Norman horse, the now-vanished Norfolk Trotter, the thoroughbred and the Anglo-Arab. The resulting mix has produced a remarkably versatile horse which works well in harness or in the field, and whose capabilities have been largely demonstrated in the showgrounds of Europe, most notably by 1990 World Champion Eric Navet and Malesan Quito de Baussy.

Two breeds of heavy horses, out of nine in France, are kept at Saint-Lô; the Norman Cob for whose breeding the place was built, and the Percheron. The Percheron is a beautiful Titan, essentially an Arab bred for strength. The Knights who went to the Crusades were, of course, mostly Normans; legend has it that they brought back Arab horses which they crossed with the sturdy Norman breed to combine grace in movement with the strength to carry an armoured man. The closed stud-book of the Percheron recognizes 17 different shades of grey.

Every branch of the French National Stud keeps a small number of Arabs and Anglo-Arabs, which are the sixth breed on the list; and last of all, a number of ponies, which the French insist on calling Poneys. This is very much a new departure for France, where the pony has been seen in the past as an inferior animal whose development was a threat to real horses.

If you want to see all these animals at their best, call in any day; but if you want the greatest free show on earth, go on a Summer Thursday. From the end of July to the beginning of September, on Thursday afternoons at three o'clock, the staff of the Haras National put on their best uniforms red for grooms, black for drivers and show off their charges in hand and in harness. When I went this year, the show fell into four parts.

First, a musical drive for the harness horses; Selle Franais both four and six in hand, an omnibus drawn by four superb Norman cobs, a dangerously spirited tandem of trotters (where the leader behaved beautifully but the wheeler objected to the view of a rival's rear), and a light trap drawn by a charming tandem of three assorted ponies. The turns are wide enough for all these to manoeuvre at a round trot, and a splendid sight they make.

After ten minutes or so, all five teams are halted no easy task with stallions, and brakes are useless on gravel paths and drawn up in the central space. At this point - it could, I think, only happen in France the public is invited to come forward and take a closer look. Perhaps three hundred people saunter around, pet the stallions, chat to the grooms. Children play tag around ironclad hooves, cameras click. The horses even the resentful trotter take it all in good part. The authorities assume, I think, that if you come to the show you must know how to behave around horses. And it works. Nobody gets hurt, nobody misbehaves, a good time is had by all. After a quarter of an hour the lady announcer asks us to go back onto the lawns, and we troop obediently back.

Next, the different breeds kept at the Stud are shown in hand, with brief explanations from the lady announcer. From thoroughbred to pony, three of each are walked and trotted across our front. The Percheron does an impromptu dance. And remember, these are no ordinary horses. These are the absolute pick of the largest National stud in France. They are magnificent, breathtaking. You could almost weep at so much power and beauty.

Last of all, the fun section. The two heaviest rigs do a last round and are driven away, and the three remaining get down to a serious speed trial. The four-in-hand achieves a respectable and thunderous canter, but the tandem of trotters disgraces itself. The leader is willing to trot at racing speed, but the wheeler sulks and won't let him. The ponies, however, save the day. Three in line with the trap bouncing behind them, they stretch out to a full gallop down the central ride; a superb piece of driving greeted with rapturous applause.

If you're going to Normandy, Saint-Lô, Town of the Horse, is a must. The stud is open every day from September through to March; there are Horse Auctions in September, Horse Shows in November, May, June and September, Jumping in early and late April, May and June, and a point-to-point in March. Every other major town in Normandy has a similar programme, every village its annual show. But for sheer value for money – I've just heard they've started charging for admission, but entry costs less than $2 – the show at the National Stud is where to spend your Thursdays.