Essex had been misled into believing that he could expect substantial support from the people of Cornwall. When he had reached Bodmin on 28 July, he found that there was no chance of supplies or recruits, and he also learned that the Royalist army was at Launceston, close to his rear, blocking his line of retreat.
He withdrew to Lostwithiel, covering the port of Fowey, hoping for support or evacuation by the Parliamentarian fleet. Essex had previously arranged to rendezvous at Fowey with the Parliamentarian fleet under the Earl of Warwick, but no ships appeared, Warwick being unable to leave Portsmouth because of westerly winds.
King Charles’s army had been reinforced as it marched, and outnumbered that of Essex by nearly two to one. The first clashes took place on 2 August, but little action took place for several days, as the King waited for all his forces to arrive and Essex waited for the fleet. On 13 August, the Royalists began to attack in earnest, occupying several outposts on the east bank of the River Fowey, making it even more difficult for help to reach Essex. A Parliamentarian attempt to send a relieving force under Lieutenant General Middleton was defeated at Bridgwater in Somerset.
On 21 August, the Royalists attacked Essex’s positions north of Lostwithiel, capturing the ruins of Restormel Castle. Royalist cavalry threatened to cut the Parliamentarians off from Fowey. Essex realised that there was no hope of relief and ordered his cavalry to break out of the encirclement. Under Sir William Balfour, they broke through the Royalist lines on the night of 31 August, eventually reaching Plymouth 30 miles to the east.
The increasingly demoralised Parliamentarian infantry fell back towards Fowey in pouring rain. They were forced to abandon several guns which became bogged down in the muddy roads. On 1 September, the pursuing Royalists captured Castle Dore, another ruined fortification which the Parliamentarians were using to anchor their lines. Essex left Sir Philip Skippon, his Sergeant Major General of Foot, in command while he himself escaped to Plymouth in a fishing boat.
On 2 September, Skippon, having been told that his infantry were unable to break out as the cavalry had done, and having been offered generous terms by the King, surrendered 6,000 infantry and all his army’s guns and train. The disarmed soldiers marched to Portsmouth in continuing bad weather, being continually robbed and threatened by local people. About 1,000 died of exposure and hunger, and 1,000 more deserted or fell sick. Charles meanwhile wheeled about and marched toward London.
This was a setback for Parliament in Cornwall, and the last major victory for the Royalists.