Prior to his creation as a viscount in 1696, Lowther had succeeded his grandfather as a
baronet, and was twice member of parliament for
Westmorland between 1677 and 1696. In 1688 he was serviceable in securing
Cumberland and
Westmorland for
King William III, and was appointed to the
Privy Council in 1689. In 1690, he was
first lord of the treasury, and he was
Lord Privy Seal from March 1699 until his death. He was badly injured in a duel in 1691. Lonsdale wrote in 1688 a brief account of events from the accession of
James II to the landing of
the Prince of Orange at
Torbay, which was later printed as Memoirs of the Reign of James II (in 1808, for private circulation) and again in 1857. The
Memoirs reveal no more of Lonsdale's part in events than his public utterances. ==Personal life==