The curtain finally falls on Downton Abbey on Christmas Day, with millions of fans already mourning its departure. Many will miss Michelle Dockery as Lady Mary, Laura Carmichael as Lady Edith, and the inimitable Maggie Smith and her acerbic one liners. But if I am brutally honest, what I will miss most is the frocks and fashion. Downton started just before World War One, but the most recent series have been set in the roaring twenties, when hemlines were raised, waists were dropped along with not so few inhibitions. The 1920s is a fashion era that was truly revolutionary, especially for women, and it remains both fascinating and iconic for…