I begin with a chuckle that turns into a lament. The Pickerskill Reports, the series in which a former public school master reminisces in a tone as lacerating as it is fond, is no more. Author and director Andrew McGibbon has declared it's a wrap with The Last Report, bringing bank-holiday merriment with its mix of the scholarly and the fantastical in a one-off special.

The series originally starred Ian Richardson, whose recruitment was a coup in itself and whose performance so matched the withering put-downs and acute insights of the script that all seemed lost for the show after his death in 2007.

Yet producer Curtains For Radio brought the series back in 2009 with another casting triumph - with his reedy-voiced enunciation and donnish demeanour, Ian McDiarmid stepped effortlessly into the other Ian's footsteps. This new play finds McDiarmid in full flight, relishing the effortless dialogue ("brandishing your braggadocio"), high-table erudition and gentle, literate comedy that can turn savage in a second.

As the 'progressive' head, Michael Feast fuses the sinister and the cynical, while Tony Gardner is the spluttering maths master Lefty, around whom Thomas Brodie-Sangster's precocious pupil, Porter, runs rings. With her girlish politeness, Elaine Cassidy is the antithesis of a villainess - until she is revealed to be working for the kind of suspect organisation beloved of 1960's TV series such as The Avengers.

Before Richardson's death, there was dangerous talk of a transfer to television, but perhaps The Pickerskill Reports is best remembered as one of radio's timeless jewels.

Very last episode of the witty social satire, blessed by a superb cast (Ian McDiarmid, Mark Heap and Michael Feast), written and directed by Andrew McGibbon. McDiarmid plays the wily head of a school which has gone through many transformations and whose past pupils duly represent the fact, whether pillars of the establishment, captains of industry or various other grades of dodgy geezer. Now meet Faye (Elaine Cassidy) who will save its site from mercantile exploitation to transform it into a beacon of the new educational ethos.