The Arundells had been on the wrong side of England's religious wars for decades. Thomas Arundell, the 1st Baron, was arrested in 1580 for his Catholic devotion and again later for accepting from the Holy Roman Emperor the title of Count, an honour the English Crown viewed with deep suspicion. He was rumoured to have been involved in the Gunpowder Plot. His son, the 2nd Baron, married Lady Blanche Somerset - daughter of the 4th Earl of Worcester, whom one historian called 'a stiff papist.' By the autumn of 1641 Parliament had issued an arrest warrant for the 2nd Baron. When the Civil War broke out the following year, he raised a Royalist cavalry regiment and rode away from Wardour to fight for the King. The castle was a 14th-century stronghold, bought by his ancestors in the 1540s, recently softened for domestic comfort but still solidly built of freestone - 'very strongly built,' as the antiquarian John Aubrey put it.

Hungerford's force outnumbered the defenders fifty to one, but found the castle 'stronger than he had expected.' He called for reinforcements from Somerset under Colonel William Strode. The castle held out for six days. Royalist propagandist Bruno Ryves later wrote that the defenders grew so exhausted that 'when the hand endeavoured to administer food, surprised with sleep it forgot its employment, the morsels falling from their hands.' The Parliamentarian officer Edmund Ludlow, arriving on 8 May, claimed little damage had been done other than to a chimney. The decisive moment came that day. The attackers rolled gunpowder barrels under one of the walls at an opening 'for the conveying away of filth' and blew a hole. Lady Arundell rejected the first terms - quarter for women and children, none for the men - but accepted when the Parliamentarians threatened to mine another wall and throw fireballs through the windows. The castle was sacked, the women carried off to Shaftesbury and then Dorchester, the loot sold cheap. Lady Arundell was released soon afterward. By then her husband had been killed at the Battle of Stratton.

Edmund Ludlow took command of the captured castle with 75 men. The first Royalist response was disorganised: Henry Arundell, now the 3rd Baron, arrived with cavalry but lacked the numbers to enforce a real siege. By November 1643 the Royalists had organised a tight blockade. Ludlow refused successive surrender demands - 'resolved to run all hazards in the discharge of that trust which I had undertaken.' His garrison ambushed farmers carrying produce to Shaftesbury market, paying them market rate for the food. The Royalists tried to plant a twelve-year-old boy inside the garrison to poison the well and beer; he was caught and confessed under threat of execution. Captain Christopher Bowyer was shot in the heel by one of Ludlow's men and died of infection a few days later. Then came Sir Francis Dodington - a Somerset landowner with what one historian called 'an unenviable reputation for ruthlessness and brutality' - bringing engineers and miners from the Mendip Hills.

The miners tunnelled for three months. Inside the castle, provisions ran low; the well dried each evening; the garrison began slaughtering their horses for food. When the first mine finally went up - either set off accidentally by an artillery match falling into the powder, or by a Parliamentarian carelessly tossing a match into the tunnel - it destroyed the west wall of the castle. Ludlow had to escape his own room through a window onto a ladder two yards below. He surrendered a few days later on generous terms: quarter without distinction, civil treatment, prompt exchange, no transport to Oxford. Two of his soldiers were arrested anyway and executed as Royalist deserters; Ludlow was briefly imprisoned at Oxford before being exchanged. By July 1644 he was back in Wiltshire as High Sheriff under William Waller. Lord Arundell had his ruined family seat slighted to prevent further military use, and the Arundells moved to Breamore in Hampshire. The 14th-century castle was never restored. More than a century later, in 1770, the 8th Baron commissioned a new Palladian house three-quarters of a mile away. Old Wardour Castle was left as a romantic ruin in the parkland of New Wardour Castle - the family's monument to the war they fought for the wrong king at the wrong time.