London Underground Poster Margaret Calkin James Chelsea Flower Show. Original vintage London Transport poster advertising Chelsea Flower Show that took place on 22, 23 and 24 May 1935 - Design by Margaret Calkin James (1895-1985) features red, blue and purple flowers in a red border. The RHS Chelsea Flower Show, is a garden show held in Chelsea since 1912 by the Royal Horticultural Society in the grounds of the Royal Hospital Chelsea, London. Printed by Curwen Press. Good condition, tears, creasing, minor staining. Country of issue: UK, designer: Margaret Calkin James, size (cm): 27x32, year of printing: 1935.