The Red Queen was developed post WWII as a defence against Divers (which was the code word for V1s) and aircraft such as the Russian Ilyushin Il-10. The Russians had learnt the hard way as to the efficacy of ground attack aircraft at the hands of Germanys one man air force; Hans-Ulrich Rudel (800 vehicles, 519 tanks, 150 artillery guns, 1 battle ship, two cruisers, a destroyer and 9 aircraft) (I suspect there is probably an lot of RAF Squadrons that couldnt equal or better that).
The ammunition had already been developed in the late 40s and obviously required a weapon to fire it. At the time it was decided that it would be better that the weapon was designed outside the UK and Oerlikon of Switzerland were picked as a potential company as they had the experience and personnel (having had the common sense to employ a lot of German scientists at the cessation of hostilities.
Taking the development outside the UK caused a lot of problems to the War Department as foreign companies couldnt be bound by such things as the Official Secrets Act etc., and if, having told them all the specifications of the weapon we wanted them to produce, they then decided not to enter into a contract, there was absolutely nothing to prevent them developing such a weapon utilising our ideas.
As a consequence the British Trade delegation and the Chief Engineer Armaments Design attended Oerlikon and somehow or another got them to enter into a contract to develop a weapon the details of which couldnt be divulged until they signed the contract.
Oerlikon duly developed a weapon with a cyclic rate of fire in excess of 600rpm. For the time, this was little short of phenomenal (this round is a lot, lot bigger than 30mm). To achieve this they water-cooled the barrel, but even then it was limited to 3-second bursts. One of the points raised by the Royal Artillery in respect of its rate of fire was the empty cases, they could see the gun pit very fast becoming knee deep in fired, hot cases.
Along with the weapon criteria it also had to meet transport criteria which is where it really didnt make the grade - and the whole unit weighed in at something just over ten tons whereas the Bofors was less than half this. Factors such as the weight and other problems eventually led to the War Department ending the contract. Oerlikon kept the weapon which had never left Switzerland and were supplied with the remaining ammunition that had been manufactured.
