Saunders Roe SR.53B Interceptor
Following the overflight of London by a Soviet bomber ( which actually turned out to be accidental - a navigation error had put him 300 miles off course ) a call was made for the immediate strengthening of air defences around the seat of government against high level/high speed threats which posed severe interception problems for the existing Javelin and Meteor night fighters cynics saw this as the politicians who had rendered the country open to attack wanting themselves to be protected first.
To meet this need an experimental squadron of 12 modified Saunders Roe SR-53 mixed propulsion fighters was rushed into service, based at Stanstead. These aircraft were virtually hand built in the interests of getting into service in under 6 months, the only variations from the original research airframe being a rearward retracting nosewheel allowing space for a primitive AI radar installation in the nose, slightly increased fuselage tankage for the Spectre rocket fuel at the expense of jet fuel tankage, provision for drop tanks to increase range when under jet propulsion, and provision for overwing Firestreak launchers in addition to the existing wingtip installation ( though rarely flown with the overwing launchers fitted ).
Given the hazardous nature of this planes propulsion systems, it is a credit to the squadron that only two were lost during their 2 years in service, both accidents occurring on the ground during fuelling. The arrival of the Lightning in service allowed these stop-gap fighters to be withdrawn.