From memoirs
"On 1 June 1956 I flew a Canberra B6 No 307 for the first airborne firing of guns from a Canberra. Four 20 mm cannons were mounted in a prototype bomb-bay pack, with the guns firing forward beneath the cockpit. A reflector gyro gunsight was fitted in the cockpit. The project leader for the gun-pack was Miss Williams and the test flights were to be her first flights in a jet. There were no problems during firing of a full load of ammunition, in bursts, into Lyme Bay."
No problems with Ms Williams either!
Wonder where you are and what you are doing now?