According to David Hemmings' autobiography, 'Blow Up and Other Exaggerations', he was first choice for the role of Uncle Henry but Ken Russell had to renege on the offer because the US film distributors did not want him. Bizarrely, Ken then cast Elton John in the role, before the singer got cold feet over wigs, costume and arduous acting lessons and asked to leave the project. The next choice was Alan Bates (who had played Birkin in the sequel, Women in Love (1969)) but he declined and the role went back to Hemmings.
In The Rainbow (1989) actress Glenda Jackson plays the mother of the character she played in Women in Love (1969). Both movies were directed by Ken Russell and both filmed adaptations of novels by D.H. Lawrence.
Glenda Jackson was only cast after the first choice declined the part because she thought the role was too small.
Source novelist D.H. Lawrence's novel "The Rainbow" (1915) is a prequel to Lawrence's "Women in Love" (1920) which were published around five years apart. Both books have been filmed as movies by director Ken Russell [See: The Rainbow (1989) and Women in Love (1969)].
The dedication billed during the picture's closing credits states that the film is "In Memory of Marion Russell" who was the cousin of the film's director Ken Russell.