[2] Operation Sigma Ltd. was formed, attracting sponsorship from Hawker Siddeley and assistance from eminent aerodynamicists, and construction of a prototype was started at the Slingsby Kirbymoorside factory.
Slingsby Sailplanes Ltd. soon went into receivership after the disastrous fire so the remaining prototype Sigma Type C was relocated to the British European Airways workshops at London Heathrow Airport (LHR).
Other equipment fitted include a retractable main wheel, speed limiting air brakes and a tail parachute housed in a compartment in the rudder.
[1] The group offered the Sigma up to further development by other parties, selecting a proposal by David Marsden a professor of mechanical engineering at the University of Alberta (on sabbatical at Cranfield Institute of Technology and a glider pilot holding records with his own glider designs such as the Marsden Gemini).
Despite the glide ratio only increasing to 47:1, its good climb rate made it competitive with contemporary Open Class gliders of the time, breaking the US 300 km triangle record in 1997 at 151 km/h (82 kn).