I think it was T21 VX275 (Mrs Hepple ) that was up over the halton ridge at maybe 2000 ft plus lots of lift from some nice black storm clouds.(not supposed to fly in these conditions).The green ball on the variometer right at the top.Opened the spoilers to descend, was still going up. Only with a full boot of rudder and a heavy side slip did the T21 drop out of the sky. Landed it back by the hangar and we them all away for he day.