During the early years of Cromwell's Protectorate, Royalist conspirators planned an uprising against the government to restore the monarchy by force. A group of conspirators known as the Sealed Knot was commissioned by the exiled Charles II to co-ordinate underground Royalist activity in England. However, the Sealed Knot proceeded cautiously and made little progress. A more militant group known as the Action Party emerged and made preparations for a series of co-ordinated Royalist uprisings around the country.
By early 1655, the two conspiracy rings were offering conflicting advice to the King and the projected uprising was postponed several times. The Sealed Knot declared that the time was not right for an uprising, but the Action Party protested against further delay and requested Charles' authority to proceed. In the resulting confusion, the western Royalists were not notified of a vital change of plan. A contingent of armed Wiltshire and Somerset cavaliers made its way to a rendezvous at Salisbury. The conspirators dispersed as soon as they realised that the uprising was postponed, but they had drawn attention to themselves and the authorities were alerted. In the following weeks, a number of leading western Royalists were arrested. Finally, 8 March 1655 was selected as the day for the uprising. However, details of the conspiracy were known to the government.
That evening a force of between 100 and 300 Royalists assembled on Marston Moor near York with the Earl of Rochester at their head. The insurgents expected sympathisers in York to open the city gates to them. When it became clear that the plan had failed, Rochester was unable to prevent panic from spreading among his followers. The insurgents fled in all directions. The uprising in other regions was no more successful.
During the night of 11 March, several hundred mounted insurgents assembled at Clarendon Park, three miles south-east of Salisbury. Penruddocke and Wagstaffe led their troops into the town before dawn the next morning. The rebels occupied the market square. The High Sheriff of Wiltshire and the judges who were conducting the county assizes were arrested in their beds. Wagstaffe wanted to hang them immediately as representatives of the hated Protectorate, but Penruddocke and others intervened to save their lives. After proclaiming Charles II, Penruddocke's insurgents rode out of Salisbury taking the High Sheriff, still in his nightshirt, as a hostage.
The rebel force of around 400 men marched westwards through Blandford, Sherborne and Yeovil calling upon the Royalists of Dorset and Somerset to rise up and join them. Very few responded. Meanwhile, government garrisons in the surrounding counties were mobilised and Cromwell appointed John Disbrowe Major-General of the West, with orders to suppress the uprising. On 14 March, before Disbrowe could take any effective action, Penruddocke's force reached the town of South Molton in Devon, where a troop of horse from Exeter commanded by Colonel Unton Croke caught up with them. After a desultory street fight, the insurgents broke and fled and the long-anticipated Royalist uprising was over.
Sir Joseph Wagstaffe succeeded in making his escape, but Penruddocke and other ringleaders were taken prisoner. They were subsequently tried for treason before a jury at Exeter. Penruddocke argued that opposing Cromwell could not constitute treason as the Protector's power had not been legally sanctioned by Parliament. However, he was found guilty and sentenced to death.
The Earl of Rochester fled south from Yorkshire in disguise. He was arrested at Aylesbury in Buckinghamshire, but escaped by bribing an innkeeper in whose charge he had been left.
Although the Royalist uprising proved ineffective, it had a profound effect on security measures within the Protectorate. Tighter restrictions were imposed upon known Royalists and they were obliged to pay the "decimation tax" to finance a new militia to supplement the regular army.