Excuse dredging up this oldish thread, but I found Spuds' recollections of Lucas Gas Turbine at Shaftmoor Lane so interesting.
I too worked there for 5 years as a 'student' apprentice, started in 1956, and after apprenticeship moved to Lucas Group Research
There was certainly some superb high precision manufacture there with some of the finest craftsmen.
I spent quite a while in the toolroom on cutter grinding as they were a cutter grinder short at the time.
A lot of the work was making small parallel and taper reamers on an Oerlikon cutter grinder, the biggest reamer would have been around 3/16", maybe up to 1/4"
The tolerances on diameter were +0.0002" -0.0000".
Eventually I had a complaint from the finishing room where they lapped the cutters to final mirror finish and size.
Most of my reamers were between +0.0000" and +0.0001" on nominal diameter and they didn't have enough material left on for lapping without them going undersize
So in effect my working tolerance had to be halved to +0.0001" +0.0002"
The fuel pump swash plates were spherically ground and then lapped on spherical laps to a mirror finish and to within a light band or so.
The pistons were similarly finished to the highest degree.
Yes, precision was abundant at Lucas's