Starting in February 1943 a committee met under the leadership of Lord Brabazon of Tara in order to investigate the future needs of the British civilian airliner market. The Brabazon Committee studied a number of designs and technical considerations, and delivered a report calling for the construction of four general designs they had studied along with members of BOAC and BEA.
In retrospect the majority of the Brabazon committee's suggestions were set up for failure. Invariably the designs were tailored to a single company, BOAC or BEA, and therefore had less appeal to other airlines. In addition they apparently failed to consider the side-effects of greatly increasing route capacity as these planes would, and thought that their passengers would continue to be the rich, the only ones able to afford air travel at the time. This led to a number of unrealistic requirements, and doomed the Type I design to carry considerably fewer passengers than it could, thereby making it too expensive to operate.
The only complete success of the Brabazon types was the Type IIB Viscount, which went on to be produced in the hundreds. THe IIA was produced in only limited numbers, as the IIB was a far better design. The Type I Brabazon was built to only one example, which was broken up along with the uncompleted second prototype. The Type III should have been a success, but a series of delays before entering service forced it to compete with newly-introduced jet designs from the US, with which it could simply not compare. The Type IV Comet almost became an outstanding success, but three mysterious crashes grounded them all for long enough that they too were outdated by the time they were able to re-enter the market.
By the 1960s it was clear that the UK had lost the airliner market to the US, and later designs like the BAC 1-11 and Vickers VC-10 were unable to address this issue. Another committee was formed to consider supersonic designs, STAC, and worked with Bristol to create the Bristol 223 design for a 100-passenger transatlantic airliner. However this was going to be so expensive to produce that the effort was later merged with similar efforts in France to create the Concorde.