From 1716 to 1731, he was Clerk of the Council of the Duchy of Lancaster, whilst also Envoy to Portugal from 1722 to 1724.
Lumley is thought to have raped Teresia Constantia Phillips at the age of 12 or 13 under the assumed name of "Thomas Grimes".
Phillips herself never realised who her attacker was and intriguingly her later autobiography was dedicated to the 3rd Earl of Scarborough.
[1] Lumley was the (anti-Walpole) Whig Member of Parliament for Arundel from 1722 to 1727 and for Lincolnshire from 1727 to 1740, when he inherited his childless elder brother's titles.
In 1723, he assumed the additional surname of Saunderson after inheriting the estate of his maternal cousin, James Saunderson, 1st Earl Castleton and was appointed a Knight Companion of the Order of the Bath in 1725.