Grimston inherited a strong interest in Hertfordshire and at St. Albans. In 1774 he stood unsuccessfully for Hertfordshire, but failed to secure the indispensable support of Lord Salisbury.
At the general election of 1784 Grimston canvassed St. Albans, but having already decided to stand for Hertfordshire withdrew at the last moment in favour of his brother, William.
You are not unacquainted that I am a wellwisher of Mr. Pitt and his Administration, and I hope you are equally convinced that I would not upon any terms give any support to a grand constitutional question which I thought subversive of our common rights in compliance to any party whatever.
And he made sure that his brother also voted.
Grimston did not stand in 1790. His alliance with Lord Salisbury bore further fruit in the British peerage of Verulam; and in return he brought in Lord Salisbury’s friend, John Calvert, for St. Albans in place of his brother.
In 1796 Grimston inherited from his maternal uncle, John Askell Bucknall, a fortune said to be over £150,000.
He died 30 Dec. 1808.
