BOAC
I think the issue of whether or not CPLS was fitted is very important, but not for Walter's reasons.
If it was fitted there is no evidence of testing, trials, an installed performance being established, EMC (for example) issue with other kit - all of which is a pre-requisite to CAR/RTS. (The Service Deviation for CPLS was issued in 1995, but that certainly doesn't preclude ZD576 being an early trials vehicle).
As I also stated a long time ago, a BoI witness confirmed "classified" kit was fitted, but similarly this is not mentioned in the CAR/RTS; despite the regulations. I merely ask if this classified kit and CPLS were one and the same. The BoI did not pursue this, even though the possibility of an EMC problem was obvious.
(I think that goes a long way toward answering Sand4Gold's request of nigegilb, who I know is referring to the fact CPLS and the precise location it was fitted have been known about for some time; certainly long before the SD emerged - which confirmed an EMC problem when using the kit. It was the repeated denials of the existence of the kit on this thread that prompted questions which revealed the relevant SDs).
Hence, failure of airworthiness process is, in my opinion, a key area. It is evidence of Organisational Fault, which the BoI were duty bound to investigate, but didn't.
Regarding my last post, Walter has posted that diagram before, his theory being the flight was intended to include all or part of the H > B leg. Therefore I think my post relevant.