About this time he was befriended by (and in 1829 took pains to promote) the Sobieski Stuart brothers, eventual publishers, in 1842, of the disputed "Vestiarium Scoticum". Lauder agreed to transcribe the famous "Cromarty MS" which remained in the possession of his family until 1936, when it was presented to Queen Mary. It is now in the Royal Library at Windsor Castle. With it is a letter in which the donor states that the book was 'given' to Sir Thomas "by the Sobieski-Stuart brothers, Ian and Charles Edward". Sir Thomas and Sir Walter Scott corresponded on this "MS" at length. A full transcript of the "Cromarty MS" can be found in Stewart & Thompson's book, "Scotland's Forged Tartans", which deals mainly with the "Vestiarium" and their opinions on it.