On route out passed through thunderstorms with much static and lightning causing intercommto go u/s. Carrying on searchlights forced the aircraft to descend to 4000ft. While over target aircraft was hit by heavy flak under starboard wing causing rapid loss of petrol. Set immediate course for British coast. Crossing Belgian coast, two starboard engines were feathered. On second approach to West Malling pilot side slipped and retracted undercarriage and made belly landing. None of crew injured.