Confessions of a Diary Secretary, ITV1, 9pm
You couldn't approach Confessions of a Diary Secretary without thinking its source material might provide any scriptwriter with problems. If you've read Westminster diary secretary Tracey Temple's confessions of her two-year affair with her boss, the less-than-svelte Deputy Prime Minister John Prescott, you'll know they amount to little more than a minor civil servant's mundane and girlish vapourings. Unique insights about the forbidden impulses that govern the human heart? Searing revelations from within the New Labour cabinet machine? Any quotes as memorably juicy as the one uttered by the scorned girlfriend of an equally bulky politician, Nicholas Soames: sex with him, she'd said, was "like having a fully loaded wardrobe fall on you with the key still in"?

No, not really. Instead, what Tracey confided to her quotidian and mildly self-deluding diary - as serialised for a six-figure sum in a Sunday tabloid newspaper - prompted The Guardian to satirise it as The Secret Diary of Tracey Temple, Aged 43 and Three-Quarters.

As that newspaper continued, Tracey's diaries "combine the giddiness of Bridget Jones with the naivety of Adrian Mole and the ruthless honesty of Samuel Pepys".

Yet it was this disarming personal honesty and unguarded mundanity that made Confessions of a Diary Secretary - along with charming and vigorous performances from Maxine Peake and John Henshaw as its central characters - such fun to watch.

In this, I suppose it mirrored the romantic imperatives of Tracey 'n' John. All they'd wanted was a bit of meaningless fun, some harmless slap'n'tickle. The affair began in the office with a jolly public slap - to Tracey's derriere, casually administered en passant by the DPM - and was further progressed by a private caress on September 11, 2001. On that day, Tracey found herself joining the rest of the world in being transfixed by TV's as-it-happened record of the horror in New York. Tearful as well as frightened that Whitehall might be the terrorists' next target, Tracey was reassured by a tender touch from her boss. You couldn't help but divine a note of bathos in her diary entry: "I will always remember where I was on that tragic day crying my eyes out while the DPM stroked my arm."

Those areas being slapped 'n' tickled became more intimate in the immediate wake of the DPM's Christmas office party. Displaying the courtly sensibilities inherent to so many bluff Yorkshiremen, John kicked things off by briskly whipping up Tracey's skirt as he walked past her while she stood at her desk.

"I didn't upset you when I showed everyone your knickers?" John gallantly inquired later when the pair were on the dancefloor, before adding: "The last thing I need is a sexual 'arassment case."

The sexual 'arassment swiftly became mutual, although no more poetic. On Tracey's first visit to John's private apartment at Admiralty House, he rustled her up a late-night sandwich, consulting the Benny Hill Bumper Book of Suave Chat-Up Lines to ask: "Are you all right with bacon - or would you like a sausage?"

Tracey's love affair was as much about minor power as casual sex: it allowed her to receive an official excuse more quickly when she produced her "Office of the DPM" business card while complaining about late-running train services to her home in Hampshire.

She also got access to better fantasies. When Tony Blair was on his hols, Tracey wrote: "I suppose I'm having sexual relations with the Prime Minister I'm like a British Monica Lewinsky - only thinner!"

She might have been; John Prescott sure wasn't. Thankfully, Tracey spared us the details.