A hot summer’s day in France, 1412. The corn stands ripe in the fields below the Chateau d’Etampes, under a cloudless sky. Peasants are skinny-dipping while nobles, weighed down by their fine, embroidered robes, go off hawking on horseback. Look closer, and you will see more: it is a window into the 15th century.

This picture is from a calendar in the Tr s Riches Heures, an illuminated manuscript painted for the fabulously wealthy Jean, Duc de Berry. Brother to King Charles V and uncle to King Charles VI, the Duke was a collector and patron, possessing such marvels as rubies weighing up to 240 carats, a variety of castles, exotic animals such as ostriches and camels and precious books, many of them religious, such as the Tr s Riches Heures (Very Rich Hours or, Beautiful Book of Hours).

Books of hours were religious works, with prayers for each hour, season and holy day. While any book before the invention of printing was a unique object, books with hand-painted pages like this could belong only to princes. The three Limbourg brothers, Paul, Hermann and Jean, worked for the Duke exclusively. They used the thinnest sable-hair brushes and expensive pigments such as crushed lapis-lazuli for the intensely blue sky, and probably worked with lenses screwed into their eye-sockets to capture tiny details such as the hairs on the dogs’ ears.

Of course, few people, even among the aristocrats allowed to see the book, could read. All the more important, then, that the image could speak for itself. Some of the information is stylised: the decoration above shows that the time of year is between Leo and Virgo - August. Phoebus Apollo, pagan god of the sun, holds the sun at noon, just above the chateau, he seat of the nobility. The nobility owed their position to the king, who in turn was held to be anointed by God, so their stronghold dominates the picture’s perspective.

Most of the rest of the scene, though, shows a lively delight in everyday life. The peasants must have been glad to strip off their filthy, verminous rags: it would have been an unusual farmworker who was not crawling with body lice. And although the nobles would have paid more for their robes than a peasant (most of whose labour was exacted as service, for no pay) might have gained in a lifetime, they would have had their share of itching. While the white coifs and underskirts would have been washed and starched by servants, the gorgeous silks and velvets were simply worn until they were too filthy or too ragged.

Indications of rank, or station, are omnipresent.The horses, like their riders, are ornately clad, with hand-sewn gold embroidery, while the oxen pull the harvesters’ cart under workaday wooden yokes. Each of the hawking party carries a different kind of bird, appropriate to his or her rank; the lady, for instance, holds a small merlin. The falconer, who leads the party, holds a hooded pair of what look like goshawks (the least noble bird) on his fist; he trails a long stick with which to put up the partridges and game birds.

Yet one can make too much of the oppressive effects of the feudal system. On a hot day, isn’t it great to go swimming?

Directory of Paris museums: www.paris-web.com French museum of arts and crafts: http:web.cnam.frmuseum Life in the French Country Houseby Mark Girouard, Cassell pound;25The Making of the Middle Ages by R W Southern, Pimlico pound;10 A History of the Crusades Vol 1 by Steven Runciman, Penguin pound;12.99