It is difficult, even now, not to be awestruck by the professionalism and unassuming good sense of Sir Adrian Boult. In the winter of 1947-48, the BBC Third Programme took the daring and controversial decision to broadcast the complete Mahler symphonies. Three of the performances were played from gramophone records; Hamburg Radio provided the Sixth conducted by Hans Schmidt-Isserstedt, the work’s UK premiere. The remainder – Nos 1, 3, 5, 7 and 8 – were prepared and conducted by Boult.

His performance of the Third Symphony, another UK premiere, is lucid and unaffected. It is also exceptionally well shaped orchestrally, no mean achievement with a work the players had never seen before. The playing isn’t flawless. Post-war raids on London’s pool of orchestral players by Beecham and Legge had robbed the BBC SO of some of its former lustre. Passengers are clearly being carried in the horn and trombone sections yet such is Boult’s professionalism the wider picture is largely unaffected.

The BBC saved none of the performances. This off-air recording was preserved on a set of acetate discs which Jon Tolansky discovered in a shop in Manchester in 1981. Kathleen Ferrier’s presence made the find doubly important. She gives an exceptionally beautiful performance of “O Mensch!”, lovingly accompanied by Boult. What’s more, transfer engineer Paul Bailey has done a remarkable job tidying up a patch of badly disintegrating sound near the end of “O Mensch!”.

The disintegration is all too apparent on the new Somm CD which couples the fourth and fifth movements of the 1947 Third with a pair of rather more familiar Ferrier recordings that illustrate her ties to two other British conductors: Malcolm Sargent, his affecting orchestration of Brahms’s Four Serious Songs, and John Barbirolli who persuaded Ferrier to overcome her inhibitions about singing in French to perform and record Chausson’s Poème de l’amour et de la mer.

Added to the Testament Mahler Third are a noisily recorded live 1951 Amsterdam Kindertotenlieder dryly conducted by Klemperer whom Ferrier disliked, and an interview she gave to CBC in 1950. Hearing Ferrier speak is interesting. Dark-voiced, careful of accent, and not afraid to correct her less than adequate interviewer, she sounds not unlike Margaret Thatcher after her voice had been lowered.