The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

Type 300 and reckoned would have a top speed of 265 mph. So different
was it that the Air Ministry, with Dowding’s backing, decided it should be
separate from the original F7/30 specification and instead given backing
and funding as an experimental aircraft.
By the autumn of 1934, the Type 300 been given another boost.
Supermarine had maintained a close relationship with engine makers Rolls-
Royce – the Goshawk engine had powered the Schneider-winning seaplanes
– but now, as Mitchell was designing his all-new airframe, a new, bigger,
more powerful engine, in development for the past two years, was almost
ready. The PV12 was a 27 litre power plant that was expected, with a bit of
tinkering, to provide more than 1,000 h.p. Suddenly, Mitchell had an engine
that could give his fighter design in excess of 300 mph. Supermarine had
been given official backing from the outset, but the PV12 – soon renamed
the Merlin – was an entirely private venture on the part of the enlightened
men at Rolls-Royce. On 5 December 1934, at a conference held at the Air
Ministry and headed by Dowding, it was formally agreed that the Merlin
should be used in the Type 300.
At the beginning of 1935, the Air Ministry issued another specification,
the F10/35, which called for a fighter capable of at least 310 mph and the
firepower of no less than six but preferably eight machine guns. By this
time, Mitchell had already decided on the ultra-thin, elliptical wings that
would give his machine such a distinctive design and it seemed that his new
aircraft, now married to the Merlin, would fulfil all the F10/35 requirements
without the Air Ministry having to go through the cost and palaver of a
formal tendering process. At the same time, at the Hawker company, the
chief designer, Sidney Camm, was also working on a new design in
response to yet another earlier specification, the F36/34. Suddenly it
seemed likely that in both aircraft the RAF had found what it needed:
modern, fast, single-engine monoplane fighter aircraft. By the summer, with
official Air Ministry backing, the development of Hawker’s and
Supermarine’s prototypes was accelerated.
By the time Göring was telling the world about the existence of his
Luftwaffe, the British aircraft revolution was underway, but even so the
path from prototype to full-scale production was a long one. It was entirely
typical of the top-heavy bureaucratic Government of the time that its
response to the existence of the Luftwaffe should be to set up a committee
entitled ‘Sub-Committee on Air Parity’.