Alwyn may have regarded the scrapping of his title music to The Running Man as a quid pro quo of working for the film industry. Perhaps, though, it was a blow to his pride in a stressful employment, which he was coming to think he no longer needed. It was time to get out ; the pop titles of The Running Man were the writing on the wall : pop, jazz, and electronic underscores were proving that expensive orchestras could be dispensed with. The classic film with the large orchestral music track was about to be eclipsed.

In any case he was becoming severely depressed. Relationships at home had been tense, and in the spring of 1963, on his doctor's advice, he left his family and moved to Blythburgh, a small village on the Suffolk coast, where he settled in a newly-built house called “Lark Rise”, evoking both his mother's birthplace in Flora Thompson's countryside and Vaughan Williams's Lark Ascending. There his grand piano was housed in a custom-built soundproofed studio, facing away from the window because he thought the bleak beauty of the river estuary would distract him from his work. To balance his reduced income, his collection of Pre-Raphaelite pictures, then unfashionable and acquired for comparatively minute sums, were auctioned at Sotheby’s. Doreen Mary Carwithen set up house with him changing her surname to “Alwyn” by deed poll, pending their marriage in 1975 after William's divorce.

Carwithen was seventeen years junior to Alwyn, whom she had met as a student of his composition classes at the RAM . She was a composer of talent ; two of her early pieces included an exquisitely lyrical First String Quartet (1945) and the colourful ODTAA Overture (1945). In 1948 she was chosen as one of two RAM representatives under a new scheme to train students in writing for film, and she spent three days a week at Denham with Mathieson. In time she contributed to over 30 films in some way or another, including full scores for Anthony Darnborough's Boys in Brown (1949), described by Antony Hopkins as “a score of which even William Alwyn would not be ashamed”, and Wendy Toye's The Stranger Left No Card (1953), which won a Cannes Film Festival award. She assisted Adrian Boult in arranging the score for ABPC's official film of the Coronation, Elizabeth is Queen (1953).