In January 1774 Greville was returned for the seat at Warwick vacated by his brother’s succeeding to the earldom; and at the same time took over his place at the Board of Trade. ‘A violent and tedious fever’ for several months prevented him from taking his seat either at the Board or in the Commons,
Fortunately for me I have had no politics since I have canvassed, for the politicians were my late friends, and those I have now to support me have not yet the refinement of trusting their politics to a man they do not esteem in preference to a man they profess to esteem, because he has varied in one point which they take up on the present occasion. I never had a more agreeable canvass ... and never thought that I was so well in the opinion of the low orders ... none of my gentle friends have polled for me.
He was returned again, and continued in opposition till he left Parliament. Only one speech by him is recorded during this Parliament—on the hawkers and pedlars bill, 1 July 1785.
Wraxall wrote of him:
Possessing like his uncle, Sir William Hamilton, an elegant mind and a taste for many branches of the fine arts, which pursuit carried him into expenses beyond the bounds of severe prudence, his resignation ... could not ... be to him in any sense a matter of indifference ... He retired during several years from court and from public life into comparative obscurity.
In fact Greville, who had a very small income, seems by 1784 to have been seriously embarrassed financially, and in December approached the Duke of Rutland about selling him the collection of pictures and sculpture ‘which has taken me twelve years to make, and during which I have had the pickings of several collections which were sold in Italy, through the assistance of Mr. Hamilton at Rome, and Sir William Hamilton at Naples’.
Greville seems to have canvassed Warwick at the general election of 1790, but retired before the poll.
He died 23 May 1809.
