As usual with CAA stuff there s nothing in writing.
if the !!!! hits the fan its up to pilots call.
everything is eventually referenceds to a FAR under 5700kg
Which say you must have a working alt, compass and clock.
Which thinking about it is all you really need for VFR.
Is still whooly as !!!! and basically lets you fly as long as nothing happens. Buts allows them to shaft you as they see fit.
BTW this is exactly the same in motor law which is all set up so that a car exiting a factory is illegal as soon as it leaves the preduction line.
MJ
Who has poked 40tonne lorrys down the road for the last 10 years and still hasn't driven a legal HGV on the road yet.