The Dorset family owned a majority of the burgages and had absolute control of the borough.

In 1754 Lionel, 1st Duke of Dorset, conveyed 14 burgages to his younger son, Lord George Sackville; and on his death in 1765 left Lord George the remainder of his holding. Shortly afterwards Lord George wrote to his brother Charles, Lord Middlesex, now 2nd Duke:1

The interest of East Grinstead requires an immediate consideration, and though Lord George understands that he is entitled to all the burgage holds which the Duke of Dorset died possessed of, yet as Lord Middlesex apprehends that under his settlement he has a claim to some of them, Lord George is willing to give up the recommending any particular friend of his own, upon the present vacancy, and will join in supporting some gentleman in this neighbourhood of fortune and independency, whose principles and connexions have induced him to act with this family.

And on 27 Mar. 1766 to John Irwin:2

I have settled my business at East Grinstead entirely to my satisfaction, his Grace having joined with me in directing Bale to convey all the votes to Wedderburn, who declares he receives them in trust for the uses of the late Duke’s will. So that there is no notice taken of the settlement upon Lord Middlesex’s marriage, the words of which certainly in law would have carried many of the votes, but my title in equity was strong ... which when I communicated to the Duke he very handsomely declared he would have no dispute with me, and immediately joined in ordering the conveyance.

Sackville controlled the borough until his death in 1785.

In 1780 Sackville bought the burgages belonging to Godfrey Webster, the second largest holder.3 These were Sackville’s personal holding, and were bequeathed to his son; the remainder were inherited by his nephew, John Frederick, 3rd Duke of Dorset, who controlled the borough after Sackville’s death.