He had already been created a Baronet, of Bulstrode in the County of Buckingham, in the Baronetage of England in 1681.
The titles became extinct on the death of his son, the second Baron, in 1702, who had no male heir: his daughter, the writer Henrietta Fermor, married the 1st Earl of Pomfret.
The estates passed to Jeffreys's widow, Lady Charlotte Herbert, who later remarried as Viscountess Windsor.
The family seat is Bottom Farm, near Grantham, Lincolnshire.
The heir apparent is the present holder's son, the Hon.