Borthwick was sent in 1424 as hostage in England in the place of James I. He was knighted in 1430 at the baptism of Alexander and James, the twin sons of King James I.[5]
Since the date of the first Lord Borthwick’s death is unknown, it cannot be stated with certainty whether he or his son, also William Borthwick, was the Scottish ambassador to England in 1459, 1461, 1463, and 1464–65.[13]
He is said to be buried with his wife in Borthwick Kirk.[14]
^Reg. Mag. Sig., "Registrum magni sigilli regum Scotorum : The register of the Great seal of Scotland, A.D. 1424-1513 published by the authority of the Lords commissioners of H.M. Treasury.", Edinburgh: General Register House, 1882, Vol. 2, p. 331, no. 1575
^Anderson, 1867:338, where he states "it is supposed in 1424"
^Brown, Peter, publisher, The Peerage of Scotland, Edinburgh, 1834: 212
^Nisbet, Alexander, "A System of Heraldry" &c., Edinburgh, 1722, facsimile edition 1984, vol.ii, chapter XI, p.177, where he states "there appears no patent in the records constituting this peerage". However in the same volume, Appendix, p.104-5 he gives a genealogy of this family and says the title was granted "in the beginning of the reign of King James II" (i.e: after 1437)
^Mosley, Charles, Burkes Peerage and Baronetage, 106th edition, Crans, Switzerland, 1999, vol.1, p.318, ISBN1-57958-083-1, who also say date & year of death not known
^Leeson, Francis L., A Directory of British Peerages, revised edition, London, 2002: 17, ISBN1-903462-65-7