And if you won't take my word for it, listen to Natalie Haynes writing on a Guardian blog a couple of years ago:
Hickson captured perfectly the fluffy ruthlessness of Jane Marple: she has wispy white hair like the mohair she's so often knitting with her softly clicking pins; the slight thickening of the voice when she's thinking; the real sense that she is, as Sir Henry Clithering describes her, "one of the most formidable criminologists in England. There she sits, an elderly spinster, sweet, placid, so you'd think. Yet her mind has plumbed the depths of human iniquity, and taken it all in the day's work".
Hickson's Marple is neither Rutherford's buffoon nor McEwan's camp schoolmarm: she is a frail elderly woman who is simply unshockable and fearless. Jason Rafiel (Donald Pleasence) has her number: "She also has a mind like a bacon slicer." He is the one who nicknames her Nemesis, the goddess of retribution, in A Caribbean Mystery. And it is the measure of a good policeman that he can recognise her brilliance in spite of her old-lady mannerisms: Chief Inspector Fred Davy (the much-missed George Baker in At Bertram's Hotel) gets her immediately, whereas poor Chief Inspector Slack (David Horovitch in The Body in the Library) is a less good judge of character.
Miss Marple's great gift is to have seen every facet of human behaviour in her village, St Mary Mead. Every new person, situation and crime is filtered through this knowledge: she is never surprised by anything. "Apparently, he's a … communist," whispers the vicar's wife of Edmund Swettenham in A Murder is Announced. "Well, yes," replies Miss Marple, thoughtfully. "Then he must be very lonely in Chipping Cleghorn."Haynes also reminds us that the first episode of The Body in the Library (Hickson's first Miss Marple) was screened on Boxing Day, two days after the the final episode of The Box of Delights was shown.
They really don't make Christmas television like that any more.