Bristol Beaufighter:

The Bristol Beaufighter was designed in spite of silly British Air
Ministry specifications (for fighters with turrets) with the simple
objects of being able to destroy anything in front of it and being
able to be produced quickly.  Since the "Beau," as it became known,
was made of tested parts and assemblies from the Blenheim and
Beaufort sister aircraft, it was quickly constructed and flown only
6 months after its inception. Production line interruption was
minimal, since it utilized existing components. The Beau, though
rather slow (330mph), had a formidable armament for its day: 4 20mm
Hispano cannon.  After it proved itself in the night Battle of
Britian, the Beau was refitted continously with new avionics to
keep it up-to-date. With Serrate passive detectors, the Beau played
an important role as an intruder during the early years of the
bomber offensive.  Beaus would bomb and rockets German night-
fighter bases to disrupt their operations and give the bombers a
chance.

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