There are no standing stones at Tankerness, but Neolithic henges and stone circles are found all over the northern islands. The circle of stones where Hunlaf and the crew of Brymsteda pit themselves against Tannskári’s people is based on the Ring of Brodgar, some sixteen miles away.

The Royal line of succession of the Picts is confusing. It is matrilineal, meaning that the Royal blood is carried through the mother’s line, even though they were ruled by kings and not queens! Also, strangely there are no recorded Pictish women’s names. One Royal Pictish lady is mentioned by name in the Annals of Ulster. However, her name, Eithne, is Irish or Gaelic. It could be that Pictish women used names the same as those given to the men, or perhaps the women were commonly given Irish names. Whatever the reason behind the dearth of female Pictish names, I have decided to use Irish names for the Pictish women I’ve mentioned.

As with Britain in the early medieval period, Norway was made up of several petty kingdoms. The names of the kings of these petty realms and when they ruled are sketchy, but I must admit that when I saw the name Hjorleif Hjorsson the Fornicator on a list of the kings of Rogaland, even though he was probably the ruler some decades earlier, I could not resist adding him into the story. He is probably a semi-fictional, legendary character anyway, but with such an epithet as “the Fornicator” I thought he definitely deserved a mention.

Kaun Solvason, the king of Hordaland, actually ruled earlier too, but I liked his name, and it was sufficiently different from Hjorleif not to be confusing.

The route Hunlaf and company travel along in Norway takes them through fjords, rivers and vast lakes. Much of western Norway is water and the history of the people there is inextricably intertwined with boats and ships. In recent years many of the waterways have been altered to generate hydroelectricity. This has meant that modern maps differ drastically from how things would have been in the eighth century. I believe the route I have chosen for Hunlaf would have been navigable by boat, but if I am mistaken, there would definitely have been other rivers that would have allowed them to head deep into the wilderness of mountains and forests.

Gullbringa, with its birch bark sewn outer covering, is actually based on a ship found in a burial at Sand, where the adventurers set off upriver. The ship burial has been dated to the seventh or eighth century AD. Log boats, whilst perhaps more likely to conjure up images of primitive tribesmen in tropical climates, were in fact common in Scandinavia and in use until well into the second millennium AD. There is even conjecture that they were used because they could double up as sledges during the winter months or on higher ground above the snow line.