Margaret Rutherford was one of a kind. Not many actresses come along with her sense of comic timing, and with her unusual looks, which was far from the 'Hollywood' glamour that was around, she was a natural for the comic roles in which she became famous.

The biography below was taken from  http://www.britishpictures.com/stars/Rutherford.htm  where you can find more.

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If Alastair Sim was the King of British character actors, then the undoubted Queen was Margaret Rutherford. With her impeccable comic timing and a face like a startled bloodhound she was a natural; the sort of player that only comes along once in a generation.

Like Alastair Sim, she was a late-comer to professional acting and chose to teach elocution. She was in her thirties before she made her professional debut and slogged away in rep. for the best part of a decade. In the mid-thirties she started to get West End roles and made her film debut in Vorhaus' quota-quickie Dusty Ermine. As a lady jewel thief, she steals the show; particularly when she does an unexpected bit of stunt work clambering about a fast moving car.

A few more low-budget movies followed until she really hit it big in theatre, first in Spring Meeting and then in Blithe Spirit. When she came back to the movies she had better roles in better films, but it took the film version of Blithe Spirit to make her a true star. Her definitive Madame Arcati was unforgettable, a weird combination of heartiness and spirituality.

After this there was no stopping her. Good films and bad films followed but she always made them worthwhile. The fifties opened with a version of another of her stage triumphs: The Happiest Days of Your Life. She spends the film battling with Alastair Sim: two school heads sharing one building. The match is a delight from start to finish and was a big hit.

The sixties brought the role she is probably most famous for: that of Agatha Christie's Jane Marple (in Murder She Said, ... at the Gallop, . . . Ahoy, ... Most Foul). By any sensible criteria she is hopelessly mis-cast – but who cares? She's wonderful even if the material isn't. This series also gave her husband Stringer Davis his most prominent role in films (as her side-kick Mr Stringer). They'd married in 1945 and he had small parts in most of her films since then.

The sixties also brought her a best supporting actress Oscar for The VIPs. In a film packed with stars she out-classed them all. She followed that with her best dramatic performance as Mistress Quickly in The Chimes at Midnight and got a Damehood in the same year.

Ill-health meant she didn't film much after that. She died in 1972 and her husband passed away the following year.

More can be found in this Wikipedia link if you wish to look.