By special request of the Prime Minister, civil servant Stephen Summerchild and philosopher Elizabeth Serafin are given the unusual brief of finding the true meaning of happiness. Twenty years after Summerchild's mysterious death Brian Jessel, a civil servant in the Cabinet Office, is asked to investigate, and he uncovers a secret world high in a Whitehall attic and a curious romance that ended in tears. 

Susan Fleetwood is wonderfully batty as the philosopher in love with stuffy Summerchild (Roger Allam). The story unfolds through tape recordings from the project left by the couple, containing all the discussions up to the time that Summerchild fell off the Admiralty Building. Endearingly played back on Jessel's son's toy tape-player, past and present flow seamlessly together in his single-minded persuit of the truth.

Robert Glenister as Jessel, Roger Allam as Summerchild and Susan Fleetwood as Serafin
   

Michael Frayn's adaptation for TV of his own novel, A Landing On The Sun, was so full of delights of various kinds that sometimes one was almost at a loss to know precisely what it was we were watching. On one level it was a detective thriller, and on another a funny and tender love story, as well as a clever satire on the civil service and its peculiar ways. It also had much to say on the elusive and for inventiveness and sheer originality it made much of what passes for TV drama seem one-dimensional and ordinary. Much of the story was told in flashback, form but with the difference that the contemporary character, Brian Jessel (Robert Glenister), a minor mandarin in the Cabinet Office in Whitehall - and that austere geographical location becomes almost a character in its own right - sees the past so vividly that he becomes part of it.

A television documentary team is poking around the circumstances of the mysterious death 20 years earlier of civil servant Stephen Summerchild (Roger Allam), and Jessel is assigned to reinvestigate the affair so that, in the time-honoured civil service way, a ministerial answer will be ready should something startling be uncovered.

The body was found in a tiny yard behind the Admiralty, and there were hints that Summerchild was somehow connected to Defence. There was, too, a personal connection. As a schoolboy, Jessel had played in the same school orchestra as Summerchild's daughter (Augusta Harris when young, and Judith Scott as the grown-up Millie) and, hanging around her garden gate, had caught glimpses of her father. He also worked in the same building as Summerchild had done, creating a mystical link with the dead man which was reinforced by renewing his acquaintance with Millie during his inquiry into her father's death.

Once into the files, Jessel begins to uncover a story which is far more fascinating than a mundane spy scandal. Summerchild had been appointed secretary of a 'unit' set up, characteristically, by Harold Wilson to produce a report on the nation's quality of life, and how it might be improved. It was to be headed by an Oxford philosophy don, Dr Elizabeth Serafin (Susan Fleetwood, at the top of her form). The scene in which she is telephoned at home by Wilson but is unable to hear what the Prime Minister is saying because of a power cut - this is 1974 - is quite hilarious. But the unit, untypically, never grows beyond this pair, plus a typist, nor does it get as far as producing a report: unsurprising, since the principals have only the vaguest idea what is required of them.

In the attic room which has been assigned to them, Jessel discovers various clues to the past, including a biscuit tin full of tape recordings of the conversations between Serafin and Summerchild as they discussed their incomplete brief. Starting with a stilted formality, these gradually become more intimate, enabling the investigator to build up a picture of an agonised love affair, and an extraordinary ménage established high over Whitehall, complete with Li-Los, cornflakes, matching dinner plates and a roof garden.

Increasingly absorbed by the tape recordings, Jessel is drawn into the fantasy world of the quality of life unit, to the exclusion of his own family life. It all made marvellous viewing. No one, including Stoppard and Pinter, is more adroit at poking affectionate fun at the labyrinthine subtleties of British middle-class life.