The early 20th-century historian W. H. Stevenson observed that: "Few things in our early history have led to so much discussion" as Æthelwulf's Decimation Charters; a hundred years later the charter expert Susan Kelly described them as "one of the most controversial groups of Anglo-Saxon diplomas". Both Asser and the "Anglo-Saxon Chronicle" say that Æthelwulf gave a decimation, in 855, shortly before leaving on pilgrimage to Rome. According to the "Chronicle" "King Æthelwulf conveyed by charter the tenth part of his land throughout all his kingdom to the praise of God and to his own eternal salvation". However, Asser states that "Æthelwulf, the esteemed king, freed the tenth part of his whole kingdom from royal service and tribute, and as an everlasting inheritance he made it over on the cross of Christ to the triune God, for the redemption of his soul and those of his predecessors." According to Keynes, Asser's version may just be a "loose translation" of the "Chronicle", and his implication that Æthelwulf released a tenth of all land from secular burdens was probably not intended. All land could be regarded as the king's land, so the "Chronicle" reference to "his land" does not necessarily refer to royal property, and since the booking of land – conveying it by charter – was always regarded as a pious act, Asser's statement that he made it over to God does not necessarily mean that the charters were in favour of the church.