Lynda Bellingham played many roles during her five-decade professional career, but became synonymous with one. "Being a mum making gravy was not quite how I had seen my career advancing," she said once. But between 1983 and 1999 that's what she did in 42 "episodes" of an award-winning TV ad. Since the early 1980s, her name was rarely mentioned in print without it being prefaced with "Oxo mum".