Scholars customarily overvalue the influence of historical truth as against historical myth

Scholars customarily overvalue the influence of historical truth as against historical myth. Thomas Innes, by exact scholarship, revalued the sources of ancient Scottish and Irish history, providing a base in which all late scholars would build. Incidentally he removed centuries of false history, and thereby destroyed the historical foundations of whig theories and the historical justification of the Hanoverian succession to the throne of Scotland. But did the political cause of Jacobitism gain anything from his work? Probably not. We may doubt whether the Chevalier de St George [The Old Pretender] even read it. In fact very few people read it. Even the greatest historian of the eighteenth century [Gibbon] was not among them. 

H.R. Trevor Roper, The invention of Scotland (2014), 71

All the myths of England come not from the Anglo-Saxons but from the Celts

For what people believe is true is a force, even if it is not true. Myth may be a driving force: such as the myth of inevitability, encountered in Calvin, or of invincibility, as at Sparta. Myth may also be the soul of history, engendering imaginative literature in poetry or prose.

Some races, it seems, are more mythopoeic than others. The myths of ancient Greece are as inseparable from Greek history as they are from Greek literature. The Anglo-Saxons, on the other hand, have been the least mythopoeic of peoples. The English have created one of the great literatures of the world. Yet, have they a singe myth that they can call their own? Almost all peoples have a myth of their own origin: a heroic age; divine descent; the discovery and colonisation of their land. The Anglo-Saxons have no such thing: no halo of romance surrounds the misty figures of their alleged leaders , Hengist and Horsa. All the myths of England come not from the Anglo-Saxons but from the Celts.

H.R. Trevor Roper, The invention of Scotland (2014), xxi