[5] Elizabeth's half-sister by their father's second marriage was Grace Smith, wife of the heroic Civil War Royalist commander Sir Bevil Grenville (1596-1643) of Bideford in Devon and Stowe, Kilkhampton in Cornwall, killed in action at the Battle of Lansdowne (1643) and mother of John Grenville, 1st Earl of Bath (1628–1701), who greatly assisted his half-first cousin George Monck, 1st Duke of Albemarle (1608–1670) in effecting the Restoration of the Monarchy in 1660.

After 1646 he obtained the small rectory of Plymtree in Devon, having in 1642 married the daughter of the then rector, whose family held the advowson, and this was confirmed to him by General Monck's influence with Cromwell.

During the Civil War his sympathies certainly leaned to the royalist side, and in 1653 he was presented by his kinsman, Sir John Granville (later 1st Earl of Bath), to the valuable living of Kilhampton in Cornwall, worth about £260 a year.

[6] After Cromwell's death Grenville sent 'the honest clergyman' up to London, where he received through George Monck's brother-in-law, Thomas Clarges, instructions to go to Scotland and ascertain his brother's intentions.

On 1 August 1660 Nicholas was created Doctor of Divinity at Oxford University, and on 1 December 1660, he was appointed by the king as Bishop of Hereford, a see which had been vacant for fourteen years.