In 1957, Michael Benthall, a director at the Old Vic, took a chance on a young woman straight out of drama school, casting her as Ophelia in a production of Hamlet starring John Neville and Coral Browne. I was lucky enough to be in the audience with my mother when Judi Dench, a velvet-voiced cherub in virginal white, made her début. An infinite variety of stage and film performances have gone by since then, but none has erased the memory of her stage presence that night.