The eight manuscripts once associated with Magnús í Vigur and now in the British Library are all kept under the shelfmark Additional Manuscript (Add.).

Six of these manuscripts were large and impressive folios taken from Iceland by Sir Joseph Banks (1743–1820), who gave them to the British Museum in the late 18th century. Banks acquired these manuscript from Ólafur Stephensen (1731–1812), who bought them for him shortly after the death of their owner Bjarni Haldórsson in January 1773. Bjarni Haldórsson had acquired the manuscripts through his wife Hólmfríður Pálsdóttir, who was the daughter of Kristín Magnúsdóttir and Páll Vídalín; Hólmfríður was the granddaughter of Magnús í Vigur and Ástríður Jónsdóttir. A seventh manuscript, Add. 4883 4to, is a smaller quarto on parchment, which was owned by the women in Magnús’s family and so reached Banks along with the more impressive commissioned folio manuscripts, but is only tangentially related to Magnús himself.

The eighth manuscript, Add. 11,153 4to, came to the British Museum later, when it was bought from Finnur Magnússon (1781–1847) in July 1837.