Having worked extensively with Malcolm Walker on Decca classical recordings from 1984 - 1994 before turning the project over to Philip Stuart for completion, I am a little puzzled about just what the 'Decca Archive' consisted of. I do know that Decca lacked the bureaucracy that helped create the EMI Archives in the first place. Aside from the legal files, to which we did not have access, Malcolm and I investigated every other source of information Decca its current or former staff had at hand - this included both Musical Records of Session (filled in by the producer) and Electrical Records of Session (done by the Balance Engineer) that were created when a work was recorded; artists cards, files and planning documents held at the Cheswick HQ, as well as the tape boxes themselves stored at the old Recording Centre before it was closed in 1997. Perhaps the reference is to files that were held the the old Embankment studio/office complex before the company was sold to Polygram in 1979. Or perhaps to any files Maurice Rosengarten possessed in Switzerland; as we know, Rosengarten helped finance and/or organize much of the Decca classical program on the Continent for many years.
Just curious - perhaps our UK members can help me out.