The first prototype (s/n TS409) was covered by Specification E.10/44 and flew on July 27, 1946, powered by the 4,300 lb (1,950 kg) s.t. Nene. The two navalized prototypes (s/n TS413 and TS416, the first of which was flown on June 17, 1947) were covered by Specification E.1/45, and were fitted with the 5,100 lb (2,313 kg) s.t Nene 3.
TS409 was later navalized, while TS413 was lost in a crash in June 1948, killing the Royal Navy pilot, Lieutenant T.J.A. King-Joyce. The type was named Attacker and 182 production aircraft Type 398 Attacker were produced:
45 F.Mk.1 and 17 FB.Mk.1 to RN (s/n WA469-WA535, WT851)
84 FB.Mk.2 to RN (s/n WK319-WK342, WP275-WP304, WZ273-WZ302)
36 "de-navalized" aircraft to Pakistan AF, s/n R4000 to R4035."