Bristol avoided gas turbine development work at first, as Roy Fedden considered that Bristol's limited wartime resources were already occupied with the enlarged generation of sleeve valve radial engines such as the Hercules and Centaurus then under development and that a useful turbojet engine was at least ten years away.
This policy changed under Frank Owner and this became one of the reasons behind Fedden's falling out with Bristol and his departure from them in 1942.
Despite the widely-admired Theseus installation in the Hermes V and its four petal nacelle with good access for maintenance, the Proteus I was designed to be buried deep within the wing of the Bristol Brabazon or the Saunders-Roe Princess,[10] leading to its unusual reverse-flow layout, with two 180 degree turns in direction.
To achieve the design power needed for the Proteus, a mass-airflow rate of 40 lb/s (18 kg/s) at 10,000 rpm was required, with an overall pressure ratio of 9.
[1][13][14] Two air inlet elbows were provided at the sides of the bomb bay, with the jet exhaust angled steeply downwards.
[7] Production engines abandoned this first stage compressor in favour of a better designed diffuser passage which recovered the mass flow, at the cost of dropping the pressure ratio to 5.35.
Nor did it show any promise for development as a turbojet in its own right, as Hooker was working on the BE.10, later to become the Olympus, which, unlike the troublesome Proteus, was a powerful and reliable success from the outset.