quality:correction, structural:summarization
1939–1952

During the Second World War Vaughan Williams was active in civilian war work, chairing the Home Office Committee for the Release of Interned Alien Musicians, helping Myra Hess with the organisation of the daily National Gallery concerts, serving on a committee for refugees from Nazi oppression, and on the Council for the Encouragement of Music and the Arts (CEMA), the forerunner of the Arts Council. In 1940 he composed his first film score, for the propaganda film 49th Parallel.

In 1942 Michael Wood died suddenly of heart failure. At Adeline's behest the widowed Ursula was invited to stay with the Vaughan Williamses in Dorking, and thereafter was a regular visitor there, sometimes staying for weeks at a time. The critic Michael White suggests that Adeline "appears, in the most amicable way, to have adopted Ursula as her successor". Ursula recorded that during air raids all three slept in the same room in adjacent beds, holding hands for comfort.

In 1943 Vaughan Williams conducted the premiere of his Fifth Symphony at the Proms. Its serene tone contrasted with the stormy Fourth, and led some commentators to think it a symphonic valediction. William Glock wrote that it was "like the work of a distinguished poet who has nothing very new to say, but says it in exquisitely flowing language". The music Vaughan Williams wrote for the BBC to celebrate the end of the war, Thanksgiving for Victory, was marked by what the critic Edward Lockspeiser called the composer's characteristic avoidance of "any suggestion of rhetorical pompousness". Any suspicion that the septuagenarian composer had settled into benign tranquillity was dispelled by his Sixth Symphony (1948), described by the critic Gwyn Parry-Jones as "one of the most disturbing musical statements of the 20th century", opening with a "primal scream, plunging the listener immediately into a world of aggression and impending chaos." Coming as it did near the start of the Cold War, many critics thought its pianissimo last movement a depiction of a nuclear-scorched wasteland. The composer was dismissive of programmatic theories: "It never seems to occur to people that a man might just want to write a piece of music."

In 1951 Adeline died, aged eighty. In the same year Vaughan Williams's last opera, The Pilgrim's Progress, was staged at Covent Garden as part of the Festival of Britain. He had been working intermittently on a musical treatment of John Bunyan 's allegory for forty-five years, and the 1951 "morality" was the final result. The reviews were respectful, but the work did not catch the opera-going public's imagination, and the Royal Opera House's production was "insultingly half-hearted" according to Frogley. The piece was revived the following year, but was still not a great success. Vaughan Williams commented to Ursula, "They don't like it, they won't like it, they don't want an opera with no heroine and no love duets—and I don't care, it's what I meant, and there it is."