Grandson of the Elizabethan hero Sir Richard Grenville, captain of the Revenge, Bevil Grenville inherited large estates in Cornwall and represented Cornwall in Parliament from 1621. Grenville actively supported Sir John Eliot in his opposition to the policies of the Duke of Buckingham, which alienated him from his father Sir Bernard Grenville. After Eliot's death in prison in 1632, however, Grenville withdrew from politics and was reconciled with his father shortly before Sir Bernard's death in 1636. He became an ardent Royalist and raised a troop of horse to fight in the Bishops Wars. Grenville served in the King's bodyguard and was knighted in July 1639.
Grenville responded to the King's Commission of Array in 1642 and raised an army of Cornish infantrymen which, under his leadership, became one of the most effective Royalist units in the early campaigns of the English Civil War. In the autumn of 1642, Grenville's endorsement of Sir Ralph Hopton as Royalist commander in Cornwall ensured the loyalty of the Cornish troops.
Grenville's infantry fought for Hopton in a series of battles in south-western England during 1642-3. At the battle of Braddock Down in January 1643, Grenville led them in an uphill charge that won the battle for the Royalists. Hopton advanced into Devon but was surprised by Parliamentarian forces at Sourton Down in April 1643. Although the Royalists were routed, Grenville made a stand that saved their army from complete destruction. The Earl of Stamford then led a Parliamentarian invasion of Cornwall in May 1643 and took up a strong defensive position at Stratton. Grenville's knowledge of the local terrain enabled Hopton to mount a surprise dawn attack on Stamford's position. After a desperate struggle to reach the hilltop, the Royalists were victorious and the Parliamentarians were driven out of Cornwall.
In July 1643, Hopton marched eastwards against Sir William Waller's army which occupied a commanding position at Lansdown Hill near Bath. Grenville's Cornish infantry stood firm when the Royalist cavalry was routed in the early stages of the battle, then Grenville led a counter-attack against the Parliamentarian position at the top of the hill. The Cornishmen succeeded in gaining the hilltop and forcing Waller to withdraw, but during the attack Grenville was wounded by a halberd blow to the head. He died from his wound the following day. Grenville's loss was a serious blow to the morale of the Cornish army, many of whom were killed in Prince Rupert's bloody assault on Bristol a few weeks after Lansdown.
References:
John Barratt, Cavaliers, the Royalist Army at War 1642-46, 2000
Anne Duffin, Sir Bevil Grenville, Oxford DNB, 2004