Armchair Thriller is a very well remembered anthology series that grew out of the Armchair Theatre strand and featured 11 serials (each made up of several episodes each) with a suspenseful theme. A great opening title sequence saw a dust sheet covered chair and a slightly scary shadowy figure approaching.
One of the serials, Quiet As A Nun, featured the character of Jemima Shore (created by Antonia Fraser). This was pretty sucessful and led to the series Jemima Shore Investigates starring Patricia Hodge. Actors appearing included Maria Aitken, James Bolam, Denis Lawson, Larry Lamb, Maurice Colbourne, Cherie Lunghi, Ian McShane, Beth Morris, Ian McKellan and a young Patsy Kensit.

The serials were
RACHEL IN DANGER
A DOG’S RANSOM
THE GIRL WHO WALKED QUICKLY
QUIET AS A NUN
THE LIMBO CONNECTION
THE VICTIM
DEAD MAN’S KIT
DYING DAY
FEAR OF GOD
HIGH TIDE
THE CIRCE COMPLEX
One further serial was made for the series, THE CHELSEA MURDERS , which remained unsreened at the time but was later broadcast in a single two hour slot with the six episodes cut obviously to fit the time slot.

production details
UK / ITV Network – Thames – Southern / 54 x 30 minute episodes / Broadcast 21 February 1978 – 10 April 1980
Creator: Andrew Brown / Theme Music: Andy Mackay / Script Editor: Robert Banks Stewart / Producers: Andrew Brown, Jacqueline Davis, Brenda Ennis