A Little Night Music was originally scheduled to open in London on November 4, 1974. Glynis Johns and Len Cariou were to repeat their Broadway roles, and Margaret Leighton, although less than 20 months older than Johns, was to play Madame Armfeldt. Unfortunately, a worldwide recession was wreaking havoc on the arts in the United Kingdom when the production was trying raise money, The production was postponed, possibly to be canceled altogether.
By December, the economy improved sufficiently that the money was raised, and the production was re-scheduled to open on April 15, 1975. By this time, however, the expected leads had moved on to other work so the roles were recast.
It was always unlikely that Johns and Hermione Gingold, who played Madame Armfeldt on Broadway, would have played together in the London production. According to Gingold's memoir How to Grow Old Disgracefully, they had not gotten along during the Broadway run. Gingold admitted that she may have been at least partly at fault. She wrote, “The leading lady, Glynis Johns, and I were not overly happy with each other. Getting along with females, as I have mentioned, is not my strong suit."
The prodution played only one matinee during previews. This is why there were only 10 previews rarther than the 12 the production would have played had it been playing a full schedule during previews.