Then more enquiries took place into the abuses of the dockyards, in which it was sought to implicate Pett.
During the next three years (1618-20) he worked under the immediate orders of the Commissioners in the New Dock at Chatham.
In 1620, Pett's friend Sir Robert Mansell was appointed General of the Fleet destined to chastise the Algerine pirates, who still continued their depredations on the shipping in the Channel, and the King thereupon commissioned Pett to build with all dispatch two pinnaces, of 120 and 80 tons respectively.

"I was myself," he says, "to serve as Captain in the voyage"-- being glad, no doubt, to escape from his tormentors.

The two pinnaces were built at Ratcliffe, and were launched on the 16th and 18th of October, 1620.

On the 30th, Pett sailed with the fleet, and after driving the pirates out of the Channel, he returned to port after an absence of eleven months.
His enemies had taken advantage of his absence from England to get an order for the survey of the Prince Royal, his masterpiece; the result of which was, he says, that "they maliciously certified the ship to be unserviceable, and not fit to continue--that what charges should be bestowed upon her would be lost." Nevertheless, the Prince Royal was docked, and fitted for a voyage to Spain.

She was sent thither with Charles Prince of Wales and the Duke of Buckingham, the former going in search of a Spanish wife.