Here we move from legend to historical fact. The necessary source for any account of the Merovingian (Merwing) kings is Gregory of Tours’ History of the Franks. In Book III he gives a vivid account of the murder of the young princes by their uncles, and the agonised grief of Queen Clotilda at the choice of “scissors or sword” that the murderers gave her. He tells us that the youngest boy, Chlodovald, escaped, “for those who guarded him were brave men”. He cut his hair – the symbolic lion’s mane of the Frankish kings – with his own hand, and devoted himself to God. He stayed for some time in hiding, but eventually returned to his own country, where he founded a monastery, which bore his name. This was St Cloud, near Paris. For the purposes of my story I have had him taken to a hiding-place in Britain.

Gregory’s history is one of battles, murders and sudden deaths, relieved by the deeds of holy men, but with very little in the way of description or social background. For an account of the Merovingian way of life – houses, occupations, countryside – I went to Gibbon’s Decline and Fall of the Roman Empire.

Europe under the Merovingians. Clovis (481–511 AD) unified Gaul, and established Paris as his capital. At his death his lands were divided between his four sons. The eldest son, the bastard Theuderic, received lands around the Rhine, Moselle, and upper Meuse. Chlodomer was established in the regions along the Loire. To Childebert went the country of the English Channel, with Bordeaux and Saintes. The youngest, Lothar, was settled north of the Somme and in Aquitaine. These territories were supposed to be roughly of equal value, but this was obviously disputable, and, as the boundaries of the “kingdoms” were not well defined, the result of the partition was a constant quarrelling – what one commentator calls “bloody competition” – between the brothers.

Pilgrimages. By the first century AD there was a system of guest houses for pilgrims to Jerusalem, on traditional routes provided with watering-places. Pilgrimages became extremely popular. As Philo of Alexandria wrote: “It is a test of faith and an escape from everyday life.” And Chaucer made gentle fun of the fact that when the good weather arrived, “than longen folk to goon on pilgrimages”. The earliest known account of a Christian pilgrimage to Jerusalem was that of the so-called “pilgrim of Bordeaux” in the early fourth century.

The Legend of the Holy Grail. The Grail was the cup or chalice traditionally used by Christ at the Last Supper. According to one legend, Joseph of Arimathea, having preserved in it a few drops of Christ’s blood, brought it to Britain, where it soon disappeared. There is a mass of literature about the quests for the lost grail, which is associated with the spear that pierced Christ’s side, and a sword. In my book The Hollow Hills I used the quest story, but with the sword as the object. That sword eventually came into Arthur’s possession, as Caliburn (Excalibur), but the spear and grail were given for safe keeping to Nimuë, Arthur’s chief adviser, who had been the pupil and then the lover of Merlin the enchanter.