Lynda Lee-Potter, the Daily Mail columnist, was once Lynda Berry from Leigh in Lancashire. Her father, Norman, who died while this book was in progress, was a miner’s son and a painter and decorator who later ran his own business. Her mother, Peggy, started her working life selling shoes. The disclosure on the jacket that the author is “married to a doctor” only hints at the tale of perilous upward mobility that lies within.

As the wife of Jeremy Lee-Potter, the son of a titled air marshal, Lynda was pitched into a world of alien cutlery, cut-glass speech and posh food such as melon and avocado. In an early kitchen culture clash, Lady Lee-Potter’s new daughter-in-law offers to steep the sliced beetroot in vinegar, as served at hot-pot suppers in Leigh.

Lynda Lee-Potter’s passage from terror and insecurity to pride in her roots is the thread that holds this peculiar patchwork of a book together. As a humorous field guide to the minute distinctions between the lower-middles and the upper-middles, the nouveaux and the popocracy, Class Act is a contribution to the social-commentary-as-entertainment tradition of Nancy Mitford and, more recently, Jilly Cooper.

Mitford and Cooper were reporting unambiguously from the front line of the second-to-top drawer. They sought to amuse rather than analyse. Lee-Potter’s motive is more complex. Her tone is lightweight, but she has had to take class more seriously because she has had to overcome it.

She is writing for people who are as she once was - those who want to get on and want to know what’s naff as opposed to “smart”. Lee-Potter is now “posh” but not yet “smart”. Hard-boiled eggs in salad are up there with Black Forest gateau in the naff ratings, apparently. I’m not sure that the late Elizabeth David, a very upper-class food writer who taught the middle classes to eat for pleasure rather than appearances, would agree.

There’s a quiz every few chapters on the lines of “Are you a snob?”, which readers from all social strata will curl their lips at and then complete furtively before embarking on the main narrative. “Are you too anxious to please?” and “Are you socially confident?” could be adapted for PSHE or citizenship as a lighthearted way of addressing the unspoken discomfort, embarrassment and disempowerment that surround class. Lee-Potter’s message, one she has absorbed slowly and painfully, is to be true to yourself. If this seems difficult, it is often class that stands in the way.

A mass-market book about class, the issue that slips off the equal opportunities agenda, is needed. The worst effects of the class system have endured because the rules have not been written down. Policy makers might talk about social exclusion, but they rarely talk about lass. The term “social exclusion” does not appear in Lee-Potter’s book (she would think it too worthy), although she may be referring to the socially excluded when she rants about “scroungers” (except when she’s ranting about royal scroungers, that is).

She’s not keen on the Ramblers’ Association either, but then she owns 10 acres, of which she’s very proud. She tells us that the Admirable Crichton, the top people’s party planner, did her daughters’ weddings. And that she gave up drinking gin and orange when Vogue deemed it naff.

The book’s first aim is to crack the secret codes of social status - the territory of connections and expected behaviour where, if you have to ask, it’s probably none of your business - with the implication that the reader too can crack them.

Lee-Potter’s advice is, she admits, “screamingly politically incorrect” and brutally frank. First, dump the regional accent. She got rid of her own on the Warrington to Euston train when she left home (it helped that she was going to drama school) and regrets that she didn’t leave her first name in the luggage rack too (“not a million miles from Sharon or Tracey”, and second in her own list of “naff names”). Perhaps losing the “y” would have done the trick.

Education is not cited as a key influence. Lee-Potter says hardly anything about teachers, except that parents from the underclass should not beat them up. Her devoted and fiercely ambitious mother may have filled the role of life-transforming teacher during her school career. It was Peggy Berry who coached her only child for the grammar- school scholarship after dabbing lemon juice on her freckles. Later she took no chances with the upmarket wedding, drugging the bride’s grandfather to stop him letting the side down. The book is partly Lee-Potter’s memorial to the parents whose love gave her the drive to succeed.

Lee-Potter is much preoccupied by the question of “true class” (consideration for and empathy with others). David Blunkett, who “more than anyone reaffirms that good breeding is not dependent on class” has it; Les Dawson (“a true gentleman”) has it; Posh Spice, whose house comes with the title “Lady of the Manor” and who jumped a supermarket queue, does not. The chapters devoted to outing “tacky toffs” who treat their servants badly are aglow with righteous indignation, but there is a cut-and-paste flavour about them.

Lee-Potter’s statement that “the system only defeats people who are phoneys or frightened or ashamed” is not the last word on class, but might serve to open a debate that is still necessary. If you don’t fancy reading a stack of old Daily Mails, you will soon want to hurl this book across the room. Still, where it works it provides a service in an area where few writers are prepared to get their hands dirty.

Geraldine Brennan