On 9 September 1476 Oliver St Clair received from his father the baronies of Roslin, Pentland, and Pentland Muir, the barony of Herbertshire, the lands of Cousland, the barony of Ravenscraig, Dubbo, Carberry and Dysart. This was confirmed by charter from James III of Scotland on 10 September 1476. However, Oliver St Clair later gave to his brother, William Sinclair, 3rd Lord Sinclair who was also known as "of Newburgh", the lands of Cousland, Dysart and Ravenscraig with the castles in return for William and his son Henry renouncing their claims to the Barony of Roslin.[1][4]
Feud with Lord Borthwick
Oliver St Clair entered into a feud with Lord Borthwick which lasted for several years after St Clair threw one of the Borthwicks over the drawbridge at Roslin Castle after dinner.[1]
Rosslyn Chapel
Oliver St Clair completed the construction of Rosslyn Chapel, which had been started by his father.[1]
Family
Oliver St Clair was married firstly to Christian Haldane, secondly to Elizabeth, daughter of William Borthwick, 3rd Lord Borthwick, and thirdly to Isabella Livingstone. He had the following children:[1][2]
George St Clair, fiar of Roslin, who married Agnes, daughter of Robert Crichton, Lord Sanquhar. He died in 1510.