The spelling of names in a history of the Viking Age presents particular problems. The same person’s name may be spelled differently in a number of different sources (Irish, Anglo-Saxon, Icelandic, Greek or even Arabic) and so complete consistency is difficult. In general I have chosen to spell place-names in Scandinavia and western Europe in the form most commonly used in those countries today (save where there is a generally accepted anglicised form, such as Copenhagen, rather than København). Elsewhere, I have generally given the Old Norse form of Viking names, with the exception of dropping the final nominative ‘-r’ (and so I use the form Harald instead of Haraldr) and some simplification of accents and diacriticals. Again, where there are generally accepted anglicised forms, such as Odin and Thor (rather than Óðinn and Þórr), I have used these. Two letters which exist in Old Norse and Icelandic may be unfamiliar to some readers – these are ð, which is equivalent to a ‘breathed’ th (as in father), and Þ, which is the same as an ‘unbreathed’ th (as in think).