Like the RCA Victor and Columbia Symphony Orchestras stateside, the National Philharmonic Orchestra (sometimes "of London," sometime not) was a nom du disque. It grew out of the eponymous RCA Orchestra based in London that producer-arranger-conductor Charles Gerhardt (1928-1999) assembled after 1960. After several years at American RCA as an engineer and editor, Gerhardt had been sent to England by George Marek, then the director of Red Seal artists and repertoire, to produce recordings for the Readers Digest label, an RCA ally at the time (as was Decca/London). For these recordings, Gerhardt engaged Kenneth Wilkerson as his recording engineer, and the late Sir Thomas Beecham's Royal Philharmonic. His conductors in the early 1960s included Fritz Reiner, René Leibowitz, Sir John Barbirolli, Jascha Horenstein, Massimo Freccia, and on occasions Gerhardt himself (whom Toscanini had admired and encouraged in his last years).
For projects of lighter music, however, Gerhardt assembled freelance musicians along with players from various London orchestras -- always a plenitude in the U.K. capital, where stringent U.S. union restrictions did not apply and salaries were cheaper, with fewer permanent jobs available nationwide. Early on he called these recording orchestras the London Promenade (basically London Philharmonic personnel) or the RCASO. In addition to concert, concerto, and bon-bon repertoire, Gerhardt arranged and conducted ten stereo LPs of film music for the Digest that were released in two volumes. Their quality so impressed Marek's successor, R. Peter Munves, that he commissioned Gerhardt to make an LP of The Classic Film Scores of Erich Wolfgang Korngold for RCA's own Red Seal label. Throughout what became a series of 15 Classic Film Scores, Gerhardt's producer was the late George Korngold, son of the composer, to whom concertmaster Sydney Sax had introduced him.
Enter the ad hoc National Philharmonic, contracted for at least a decade by Sax. Under Gerhardt's direction they played his arrangements of motion picture music by Max Steiner (numerically the all-time champ), Bernard Herrmann, Franz Waxman, Miklos Rozsa, Dmitri Tiomkin, John Williams (all three Star Wars scores), Alfred Newman, Victor Young, John Barry, Leonard Rosenman, and of course Korngold.
Subsequently Chesky Records leased some of the earlier Readers Digest material for a superbly remastered and custom-pressed series of discs, on one of which the name National Philharmonic first appeared, dated 1967. The actual year of origin, however, seems to have been 1972, starting with the RCA Korngold collection. That trailblazing film series was completed by 1985, although Gerhardt himself recorded a Wagner collection with the NPO for Chesky as late as 1995.
The National Philharmonic, however, ceased to be RCA's or the producer's personal orchestra when Gerhardt replaced Sax as concertmaster, feeling that his playing had deteriorated beyond repair. Thus, Richard Bonynge conducted the NPO extensively for Decca/London recordings of opera and ballet; so did Riccardo Chailly, Bernard Herrmann, Nicola Rescigno, Gianandrea Gavazzeni, even Sir Georg Solti. James Levine led operas and recital discs for RCA and Sony. Also for Sony, Leopold Stokowski led the NPO in final-period recordings till the day before his death in 1977, at the age of 95.
After his farewell Wagner CD, Gerhardt retired to California, where he died four years later. From the available evidence, his informal NPO also gave up the ghost after 25 years, when the classical market went soft worldwide in the later '90s, and London players with permanent posts clung to them like becalmed sailors, waiting for a breeze to rescue them from irrelevance as a professional breed.