A zealous royalist, he was in 1643 appointed Lieutenant-General of the King's forces in the counties of Lincoln, Rutland, Huntingdon, Cambridge, and Norfolk, and soon after taking up this command was accidentally shot near Gainsborough, when being carried off in a pinnace as a prisoner to Hull by the Parliamentary Army.

He married in 1601 Gertrude, eldest daughter and co-heir of Sir William Reyner, of Orton Longueville, Co.Huntingdon.She survived her husband six years.
The second Earl was Henry Pierrepont, who was born in 1607.

From 1628, when his father was given the earldom, he was known under the style of Viscount Newark.

In that year he was elected Member of Parliament for Nottingham, and he represented that constituency until 1641, when he was summoned to the House of Lords in his father's barony as Lord Pierrepont.

He, too, was an ardent supporter of the King, and was a member of His Majesty's Council of War at Oxford.