DESPITE not owning any land north of Yorkshire, the Dukes of Richmond for long received a handsome payment on every chaldron of coal shipped from the Tyne. In the early 18th century the bounty brought in £5,000 a year - enough to comfortably support an aristocrat and his family.

This strange situation - an outrage if you consider the meagre wages and harsh working conditions of the miners - arose because Charles II decreed in 1677 that a levy of 1s (5p) per chaldron on the Newcastle coals, which had been paid to the Crown for almost 100 years, should go to his son, the five-year-old Duke of Richmond.

Highlighting the so-called 'Richmond shilling' in a new book*, David Morris notes: "In effect the King was giving the young duke a substantial slice of the Crown's revenue, which increased in direct proportion to mining and manufacturing." By the end of the 18th century it was worth £21,000, a sizeable chunk of the Crown's entire tax income.

No doubt hard bargaining was required when the Duke was persuaded to surrender the levy to the government in 1799. In return the Duke accepted an annuity of £19,000, later converted to a share in Government stock. The coal levy itself was scrapped in 1831.

Morris cameos the Richmond shilling in the broader story of the Honour of Richmond - a scattered but mighty estate. Originally focussed on the castle, it comprised 400 manors in 11 counties, stretching from Yorkshire down eastern England to London. The third richest post-Conquest estate, it was the gift of William the Conqueror to Alan Rufus, a Breton who advised him on the invasion of England and commanded the rearguard action that defeated Harold at Hastings.

It was Alan who built the castle. Judging that the former centre at Gilling, used by the Earl of Mercia, would be inadequate against marauding Scots, Danes or Anglians, he selected a hilltop site near the former Roman stronghold now known as Catterick. One of Britain's first stone castles - as distinct from a wooden stockade - it lacked today's keep, erected a century later. Alan named it 'Riche Monte', meaning strong hill.

As Morris, a Richmond resident of long standing, observes: "In time the name of Richmond gained much favour . . . There are many Richmonds in the world today, and the orgin of their name can only be found on the site of Count Alan's castle in North Yorkshire." So much for that uppity Surrey Richmond.

Alan tenants were required to guard the castle, where they served two-month stints. Perhaps more memorable is that Alan and his brother, who succeeded him briefly, both, in Morris's words, "enjoyed the favours" of a nun. Though her identity was initially unknown to them she turned out to be the daughter of the vanquished Harold - posthumous salt in his fatal wounds.

Notable names among the ten or so Richmond earls over the next six centuries included John of Gaunt, a prominent son of Edward III. As a young man he made Richmond castle his main base, from which he often hunted in forest of Swaledale manor, itself covering 52,000 acres. The link is recorded by Chaucer, in lines which also appear to sanctify John, who befriended and supported him:

Gan quickly homeward for to ryde Unto a place ther besyde... A long castel with walles whyte, By seynt Johan on a riche hil.

Though Gaunt's military and parliamentary activities drew him to London, where he lived at The Savoy, a beautiful mansion at Charing Cross, one of his last acts as Richmond's earl was to grant the town's Franciscan friars the right to take fuel from the forest.

In 1485, the convoluted Wars of the Roses brought Henry Tudor, the great great grandson of John of Gaunt, to the throne as Henry VII. The only Earl of Richmond to become monarch, he glorified his Yorkshire title in the name of his sumptuous new house by the Thames - Richmond Palace, whose remains still survive.

An even bigger figure, Henry VIII, enters in 1525 when he created his six-year-old son, by a maid to his wife, Catherine, the Duke of Richmond. In 1675 Charles II followed suit by conferring the then vacant title on his three-year-old son by his mistress.

The same fortunate infant who first received those coal tithes, it was this Duke who launched the present line of Richmond dukes, now stretching to ten. In 1697 he also converted a hunting lodge at Goodwood, Sussex, into the mansion that has been the family seat ever since. When the 71-year-old tenth Duke, recently opened the new visitor centre at Richmond castle, which is still owned by his family though it has been leased to the state since 1910, it was his first visit to his titular town.

Through other titles they often held, the medieval Richmond dukes enjoyed a wide choice of castles, such as Lancaster, Kenilworth and Leicester. When the head of the Honour of Richmond last lived at Richmond isn't clear. But Morris notes: "The French aristocrats who held the Honour were prone to give preference to manage their estates and affairs in France." Their frequent absence meant that "by the 14th century the Honour was in an alarming state of decay."

In 1300 it still embraced estates in seven counties. But before and after that, gifts of land and homes from the Honour by the Crown, which held the property during breaks in succession, whittled the Honour dramatically. Today it exists largely in name only. But Richmond castle, the title, and 'Glorious Goodwood' - the house and the racecourse, to which successive Dukes of Richmond have devoted great attention - form a striking legacy. It is all splendidly served in David Morris's meticulously researched and lucidly written account.

* The Honour of Richmond by David Morris (Sessions of York, hb £15, pb £10).