The peer, the mistress & the vanishing spin doctor

You have to hand it to Andy Coulson. Having stuck out the phone-hacking scandal for several months, David Cameron's communications chief chose the perfect moment to hand in his resignation and do a runner on Friday from Downing Street.

Yesterday, courtesy of the Sunday Mirror, came one of those tricky stories that Tory spin doctors have to deal with occasionally: namely, a senior Conservative peer, so senior that most of the country have never heard of him and have no idea what he looks like, is accused of having an affair behind his delightful Church-going wife's back with another woman.

The Tory peer is Lord Strathclyde - Conservative leader in the House of Lords and, as such, a member of the Cabinet - and the "other woman" is Birgit Cunningham, so well connected that she once shared a flat with Liz Hurley and had a fling with the Hollywood actor Kevin Costner.

In recent years, however, she has fallen on hard times. According to the Mirror, she is a "penniless single mum" living in a housing association flat in London.

The delightful wife is Jane, whom he married in 1992 and with whom he has three daughters. Needless to say, they divide their time between a family estate in Ayrshire and a comfortable townhouse in Westminster.

Unfortunately - if you take Birgit's story at face value - Jane spent rather too much time in Ayrshire and was unaware that the 2nd Baron Strathclyde  - born, incidentally, Thomas Galloway Dunlop du Roay de Blicquy Galbraith - was using the townhouse for rumpy-pumpy with Liz Hurley's one-time flatmate.

This is Birgit, talking to the Mirror about one of her early soirees with Strathclyde, back in 2005: "He led me into one of the dining rooms [note that: one of] and poured me more wine... There were pictures of his family everywhere and young children's toys on the floor. We didn't talk for long and he was all over me like a rash and we did it there on the sofa."

There is much more, of course, described in gruesome detail on pages 4, 5, 6 and 7 of yesterday's Mirror, the text dotted with "pull quotes" along the lines of: "He soon began kissing me and rubbing my leg" and "He seduced me in a filthy flat that stank of chip fat".

The reason why Birgit decided to spill the beans was, she said, the hypocrisy of it all. The government preaches family values and yet here was a Cabinet member "sneaking away from his wife to have sex with me".

And the reason why Andy Coulson is well out of it is because, let's face it, it will only get more difficult.

Firstly, in these situations, the communications chief's job is to persuade the wife - assuming the mistress's story is vaguely accurate - to do the obligatory "I stand by my man" photo op. This is where she and hubby pose together on the front steps of the family home - preferably arm in arm, and dressed in matching corduroy trousers and Wellington boots - and vow that nothing, not even Birgit, can come between them.

Then, just when the wife thinks it's all over, along comes part two of the Sunday newspaper's expose. This is where Birgit, now relegated to pages 11, 12, and 13, fulfills her contract by offering further details, perhaps along the lines of the famous quote from a young lady who said of having sex with Tory grandee Nicholas Soames, a Conservative of similar proportions: "It was like having a wardrobe fall on you with the key still in it".

You're well clear of it, Andy. ·