I would have given anything for a pair of orange floral flares and a purple crocheted waistcoat on Tuesday night when Chorleywood Bookshop asked me to do a live interview with fashion guru, high street saviour and Watford girl made good Mary Portas.

Some 400 mainly female fans (Mary’s, not mine, in case you were wondering) crammed themselves into Dr Challoner’s school hall in Little Chalfont to hear Mary read from her memoir of growing up in North Watford and getting into trouble at St Joan of Arc convent school in Rickmansworth during the 1970s.

It’s a delightful book, beautifully written in deceptively simple prose that is by turns laugh-out-loud funny (remember Vesta curries, Angel Delight mousse and Rimmel glitter eye-shadow?) and profoundly moving in its description of life for the teenage Mary after the sudden deaths of her parents - but thankfully without a hint of self pity.

Judging from the distances that several audience members had travelled, the queen of shops is also queen of many hearts, but funnily enough, I wasn't looking forward to the evening.

You see, much to my surprise, I’d had a rather bruising encounter with Mary (and later with her publicist) on the phone the day before - all to do with her apparent refusal to answer questions about shopping trends.

Refusal? Isn't that what she’s famous for? Going undercover into failing shops and turning them around; inspiring independent retailers to get back on the high street and recreate the sense of community she knew as a child? Isn't that precisely why we love her?

I muttered something about Mary’s knowledge of retail being her USP (unique selling point) and it being rather disingenuous of her to think a publisher would commission a childhood memoir from her without it, but no, her PR woman’s indignation knew no bounds: Mary would limit herself to questions about her book and that was that.

So, instead I did what most celebs hate and we journalists love and kept my questions personal: Will St Joan’s ever ask her back to present the prizes on speech day? What was her worst fashion faux pas? How did she bounce back after her bereavements?

On the night, the tall redhead was a joy, regaling her audience with enough anecdotes to fill a designer handbag, from her mimicry of camp window dressers at Harrods and Harvey Nic’s, to the honeyed tones of her Irish mother asking (or rather telling) the priest ‘You’ll have another slice of my coffee and walnut cake, Father?’ And you know what? Once I’d finished my interview, every single question from the floor was about shops, retail and running a fashion business.

And did Mary answer them wittily, helpfully and with good grace? Of course she did.