first Earl of Portmore was the elder son of Sir Alexander Roberston
of the Strowan family, Perthshire, who settled in Holland.
Sir David acquired a considerable property and adopted the name
of Colyear. In 1674 he joined the army of the Prince of Orange as
a volunteer and ultimately obtained command of a Scottish regiment
in the Dutch Service. At the revolution he accompanied William of
Orange to England in 1689 as Lieutenant Colonel. For his distinguished
services in the Irish campaigns of 1689 and 1690 and afterwards
in Flanders, on 1st June 1699, he was created a Peer of Scotland
by the title of Lord Portmore and Blackness.
He has been described as one of the best Foot Officers of his time,
and a man of honour. At nearly fifty years of age he married Catherine
Sealey, Countess of Dorset, a former mistress of James II.
In 1702 he was promoted to the rank of Major General and on 27th
February 1703 took command of the 2nd Regiment of Foot, The Queen’s.
In that same year he became Earl of Portmore, Viscount of Missington
and Lord Colyear.
In the war of succession in Spain he served under the Duke of Ormonde
as Lieutenant General and in 1710 was raised to the rank of General.
In 1712 he served under the Duke of Ormonde in Flanders and became
a member of the Privy Council and was made a Knight of the Thistle.
In August 1713 he was appointed Governor of Gibraltar. In 1727 he
assumed command when Gibraltar was besieged by the Spaniards. He
died at Gibraltar, on 2nd January 1730.