The aircraft was not BISZ, it may have been BIEJ and the picture was taken at Battersea. MrsT was sometimes picked up at Battersea but often down at a temporary landing site in Canary Wharf area. The authorities were very worried about the IRA in 1987 so it was always in 12 seat fit with Mrs T!, Denis and security. There was one other site in Central London which was prepared but not used. It required the crew being checked out on the backwards Category A take off.