With the outbreak of civil war in 1642, the royalist Granvilles found themselves at odds with the parliamentarian town’s-folk of Bideford. Sir Richard Grenville (grandson of the last mentioned Sir Richard) became a prominent royalist leader and rallied the Cornish behind the crown. Meanwhile, the Bideford-based Sir Bevill Grenville led royalist forces against his former neighbours in various skirmishes. He also formulated an unsuccessful plot against them, following the failure of which he withdrew to Stowe. Understandably, for Bideford’s relationship with the Granville family must have been strained.

The Parliamentarians under Sargeant-Major-General Chudleigh secured Bideford by building two forts, West-of-the-Water and East-of-the-Water (a further fort was built to protect Northam). The East-of-the-Water fort was the more significant one and was equipped with eight cannons. It served as Chudleigh’s command centre and now bears his name as Chudleigh Fort.

On 2 Sep 1643, after a desperate struggle that, it was said, left the victor’s swords “blunt with slaughter,” Bideford and Barnstaple both surrendered to Royalist forces.

1651 saw the end of the war, but not before there had been a change in the Granville’s fortunes.
On 5 Jul 1643 the war claimed the life of Sir Bevill at the Battle of Lansdown, a considerable monument marking the field near Bath where he fell. After Sir Beville’s death, his Royalist mantle was seized by his son John. A transaction from 1650 suggests the Granvilles mortgaged properties, summarised as the ‘Burrough Manor Barton, and demesnes of Bydeford,’ to help finance the Royalist cause. Sir Richard, despite his efforts on the Royalist behalf, had fallen from favour within their ranks and ended his days in France.

In 1660, Sir John Granville played a significant role in the restoration of the Monarchy (his mother’s half-sister being the mother of the prominent parliamentarian General George Monk). He then took the family’s power to a second zenith under Charles II, earning the title Earl of Bath, before another fall from grace left the family embroiled in legal wrangles and debt.