Howell graduated from Goldsmiths College, London in 1969 and began designing, making and selling shirts from a Blackheath flat in 1972. Encouraged by orders from Joseph and US retailers, a franchise shop opened on South Molton Street in 1976, followed by her first independent shop in 1980. Jack Nicholson insisted on wearing his own Margaret Howell corduroy jacket in The Shining, prompting an order for 12 duplicates from Stanley Kubrick; in 1982 Grace Coddington chose a Howell piece as Dress of the Year.
Keynote designs are her variations on the tailored shirt, lace-up shoe, duffel coat and trench, with an androgynous, timeless quality. The MHL line arrived in 2004 and the Margaret Howell Plus collaborations from 2010. Today the company employs some 500 people across more than 80 locations, including Paris, Florence and Tokyo. Howell was appointed CBE and made a Royal Designer for Industry in 2007.