By 1950, Neagle was at her zenith as Britain’s top box-office actress, and in that year she made what reputedly became her own favorite film, Odette, co-starring Trevor Howard, Peter Ustinov, and Marius Goring. As Odette Sansom, she was the Anglo-French resistance fighter who was pushed to the edge of betrayal by the Nazis.

Going from this real-life British heroine, she went straight on to playing Florence Nightingale in The Lady with the Lamp (1951); Kay Francis had previously portrayed Nightingale in a 1936 American film, The White Angel).

Returning to the stage in 1953, she scored a major success with The Glorious Days, which had a run of 476 performances. Neagle and Wilcox brought the play to the screen under the title Lilacs in the Spring (1954), co-starring Errol Flynn. In the film she plays an actress knocked out by a bomb, who dreams she is Queen Victoria and Nell Gwyn – as well as her own mother. As she begins dreaming, the film switches from black and white to color. In England, where Neagle had top billing, the film was reasonably successful. In the United States, however, where Flynn had top billing, the title was changed to Let's Make Up, and it flopped, with limited bookings.

Neagle and Flynn reteamed for a second flm together, King's Rhapsody (1955), based on an Ivor Novello musical and also starring Patrice Wymore (Flynn's wife at the time). Although Neagle performed several musical numbers for the film, most of them were cut from the final release, leaving her with essentially a supporting role. Shot in Eastmancolor and CinemaScope with location work near Barcelona, Spain, King's Rhapsody was a major flop everywhere. Neagle's (and Flynn's) box-office appeal, it seemed, was beginning to fade.

Neagle's last box-office hit was My Teenage Daughter (1956), which featured her as a mother trying to prevent her daughter (Sylvia Syms) from lapsing into juvenile deliquency.

Neagle and Syms worked together again on No Time For Tears (1957), also starring Anthony Quayle and Flora Robson. As directed by Cyril Frankel, this was the first film for over 20 years where Neagle was directed by someone other than Herbert Wilcox. Set in a children's hospital, the film features Neagle as a Matron dealing with the problems of the patients and the staff, notably a nurse (Syms) infatuated with one of the doctors (George Baker).

With her husband, Neagle began producing films starring Frankie Vaughan, but these were out of touch with changing tastes, and lost money, resulting in Wilcox going heavily into debt. Neagle herself made her final film appearance in The Lady is a Square (1957).

Herbert Wilcox was bankrupt by 1964, but his wife soon revived his fortunes. She returned to the stage the following year and made a spectacular comeback in the West End musical Charlie Girl. In it she played the role of a former "Cochran Young Lady" who marries a peer of the realm. Charlie Girl was a phenomenal success that ran for a staggering six years and 2,047 performances. It earned Neagle an entry in the Guinness Book of World Records for her enduring popularity.

Two years after Charlie Girl – which she also performed in Australia and New Zealand – Neagle was asked to appear in a revival of No, No, Nanette, which she had done onscreen three decades earlier. Later, in 1975, she replaced Celia Johnson in The Dame of Sark and, in 1978 (the year after her husband's death), she was acting in Most Gracious Lady, which was written for the Silver Jubilee of Queen Elizabeth II.