He became Member of Parliament for Chester in 1754 and continued to represent the city until 1761, when he became Baron Grosvenor and was elevated to the House of Lords.

However, when the Tory Earl of Bute became Prime Minister the following year, Grosvenor changed his allegiance.

He voted against Fox's India Bill in 1783 and was rewarded by William Pitt the Younger with title of Earl Grosvenor the following year.

[1] However, the marriage was not happy, and Henrietta had an affair with Henry, Duke of Cumberland, the younger brother of George III.

The couple were discovered in flagrante delicto in 1769, which led to Grosvenor bringing an action against the Duke for "criminal conversation" (that is, adultery).

[8] But Grosvenor was also known to be guilty of adultery himself, regularly seeking out prostitutes around Leicester Square,[9] so he could not sue for divorce.

The couple separated and he settled an annual allowance of £1,200 (£150,000 in 2015)[8] on his estranged wife,[1][3] who entered the demi-monde and was a leading member of The New Female Coterie.

[10] Grosvenor died at Earls Court in 1802 and was buried in the family vault at St Mary's Church, Eccleston.