Operation Sigma Ltd was formed, in February 1966, by leading members of the British gliding movement to produce a British designed and built open-class World Championship sailplane. The target was to win the World Championship’s in 1969, and the directors were G.E. Burton, M.I. Gee, H.C.N. Goodhart, F.G. Irving, B.S. Shenstone, W.N. Slater, C.O. Vernon, L. Welch, and K.G. Wilkinson.

For the first nine months there were no staff on the company payroll and the work was all done by members of the Board. This involved research and the raising of the necessary capitol. The decision by the International Competition Committee to hold World Championships in 1968 and 1970 instead of 1969 caused the Sigma board to set the target at the 1970 Championships.

In November 1966 N. Beckett was appointed aerodynamicist to the project and this was followed, in January 1967, by the appointment of J.L. Sellars, the designer of the Slingsby T.53, as Chief Designer. Her was based at Kirkbymoorside where Slingsby Sailplanes Ltd provided office and workshop space following thei appointment as sub-contractors for the construction of the Sigma prototype. Slingby’s provided design and works staff under contract to Sigma, and construction of the Sigma A and B prototype sailplanes commenced at Kirkbymoorside in the spring of 1968.

Work proceeded to schedule until November 18 when Sigma lost everything in the fire at Slingsby’s. The partly constructed wings and fuselage of Sigma A were completely destroyed and the Design Office was gutted. The Sigma Board decided to continue the project, and wok started to re-draw the lost drawings although many areas of the structure were re-designed to simplify manufacture, particularly the wings, in the light of experience already gained.

Construction of the jigs for the Sigma C commenced in Slingsby’s joinery works and detail parts were made again although it was realised that the 1970 Championships target was not likely to be achieved. It was suggested that construction of the wings should be sub-contracted but this was decided against due to cost. As a result, J.L. Sellars resigned from the project in July 1969. The bankruptcy of Slingsby’s later in the same month then caused a complete cessation of work on the prototype, apart from one person acting as liaison with sub-contractors and looking after the project’s assets.

The Sigma Board decided that the project should continue, and alternative premises were sought. British European Airways then offered space in some empty workshops in London Airport, and these were accepted. The one remaining member of the staff crated up all the jigs, drawings and parts, and sent them in two trucks to Heathrow where Lorne Welch took over the whole project, as full-time Project Director, in September 1969. Construction started again with facilities and staff sub-contracted from B.E.A.