project was considered a failure and the pair of flying boats were scrapped in 1951. Saunders-Roe considered the Shetland to have not resembled the flying boat that they sought to develop, but was otherwise a useful learning experience; even prior to the Shetland, the company had wanted to develop a more revolutionary flying boat. During 1943, the chief designers of Saunders-Roe and Short had collaborated to produce a preliminary design specification for an innovative large flying boat. This design specification defined various criteria for the proposed aircraft, which would be the largest all-metal flying boat ever built; performance criteria included a weight of 140 tons, a pressurised 'double-bubble' hull, a 214-foot wingspan, a height of 55 feet 9 inches, and a length of 148 feet. The proposed aircraft would be capable of a cruising speed of 340 MPH at an altitude of 37,000 feet, a range (dependent on payload) of 5,190–3,640 miles, and be outfitted with luxurious accommodation for a total of 104 passengers. Selection and delays During 1945, in response to an approach made by the British Ministry of Supply, which had been seeking design submissions from aviation companies for an envisioned new long range civil flying boat, which was to operate in BOAC's fleet to operate its transatlantic passenger services, Saunders-Roe decided to submit a bid based upon the earlier collaborative design specification. Following evaluations of a range of different propulsion methods and configurations, the design team selected the undeveloped Bristol Proteus – one of the first turboprop engines – to meet the enormous power requirements of the proposed giant flying boat. In May 1946, the bid made by Saunders-Roe was selected as the winner, leading to the company receiving an order for the production of three SR.45 flying boats. Work on the SR.45 commenced almost immediately upon receipt of the order. From an early stage in development, progress on the programme was subject to schedule overruns and higher than projected costs being incurred, leading to scepticism of the flying boat's viability within the House of Commons, which was being increasingly regarded as a high-risk initiative with unreliable costing. Specifically, designing and testing of the airframe, as well as the independently conducted development of the Proteus engine to power the SR.45, had been major contributors to the higher-than-expected costs. In 1951, BOAC re-evaluated its standing requirements, and determined that the airline presently had no need for the Princess,