In 1937, the first P.82 prototype, "K8310", was rolled out. Furnished with a 1,030 hp (768 kW) Rolls-Royce Merlin I and initially lacking its turret, the aircraft bore a great resemblance to the contemporary Hawker Hurricane, although it was at least heavier. On 11 August 1937, "K8310", which had recently received the name "Defiant", conducted its maiden flight. This initial flight, piloted by Boulton Paul's chief test pilot Cecil Feather, occurred nearly a year ahead of the rival Hotspur but still without the turret. Official acceptance trials did not commence until nine months later. On 30 July 1939, the second prototype, "K8620", equipped with a Merlin II engine and a full turret, conducted its first flight. "K8620" had received various modifications over the first prototype, such as telescopic radio masts and revisions to the canopy and to the undercarriage fairing plates; implementing these improvements had incurred delays to the completion of the second prototype.