I agree with mds. Much as I like the BG preamps, without being quite as uncritical of them as some other people, any suggestion that the entire output of Decca has used that design is ..er.. a gross exaggeration!
Decca started in the late 1920s - somewhat before the BG or any other solid state preamp came into being. Arguably, it's "golden age", particularly for classical, was the 1950s and 1960s when most of their recording gear glowed. (Not that the two are necessarily linked - I couldn't care less whether a mic/pre/mixer uses valves or not, as long as it sounds good.)
For that matter, nowadays, not all Decca recordings are made by people using identical gear - and not all the people making their records choose/use BG preamps on every recording they do so it's no more true now than ever it has been.
It's true that some of the Decca catalogue uses the BGs, or their ancestors, but not by any means all of it, and not necessarily even the greatest highlights. (Imo of course.)
The BGs are good preamps - not technically immaculate but who cares - they're sonically very nice and, for a change in this wonderful commercial world, are generally good value. I'd say that they, and Mick, have well earned their reputation and stand up for themselves without needing the kind of "validation by association" that I seem to see so many people (not necessarily in this thread) seeking for their decision to buy them. Evaluate gear with your ears, not your keyboards. And trust your own opinions.
OK, rant over - having got a bit of a grumble out of my system, I'm going for a cold drink - it's way too hot here and I can't seem to shake a dose of the flu!
(And anyone with even a passing interest in recordings of vocal/piano music should check out the Rilke disc that Plush mentions above - it's superb! And I can only wonder what would the future have brought from this wonderful singer. LHL is sadly missed here.)