From the days (around 1962) when we first got the Trident as when it had the basic auto/pilot of 2 pitch and 1 roll or was it 1 pitch and 2 roll (it was a long time ago) I as an electrical /instrument fitter on the Trident 1s in the central area and saw its development to the Cat 3 standard and until its demise, it was an expensive piece of kit everything in triplex except for the Air data computers the gyros were costed at £3000 each and you could by a small house for that at that time and the aircraft had to have fully separate generator electrical supplies but when it was working and it became reliable it did save alot of diversions to Stanstead ,Gatwick and airfields further north with the ground engineering having to go and retrieve them when there was fog at London, and passengers when they landed in fog at London were left wondering how they were getting home as the fog was making drivng hazardous and most traffic was at a stand still.We were very proud of it .