It is the publishing phenomenon of the year even though it is, reputedly, on the very naughty edge of saucy.

On a scale of one to 10, when one is tame and 10 brings you out in hives, this is reckoned to be 11.

It is Fifty Shades of Grey. Not as you might think, a Dulux paint chart but a novel, the first part of a trilogy that centres on the sex lives of an innocent young woman and a worldly, fabulously wealthy, unbelievably good looking man who can also play the piano.

I had resisted buying That Book because (a) it had been dubbed mummy porn (b) the literary reviews were not terribly complimentary and (c) my mum might find out.

Everyone – well, women – was asking me what I thought of it. Interestingly, no one asked if I had read it. There was an assumption I had.

But honestly, I think the idea of it brought out my Victorian streak, the one that prompts me to knit socks if I see naked table legs.

So why did I suddenly buy That Book? Impulse and inevitability.

We went to Oxford for the day, stopping off in Reading the previous evening to watch our son in his outdoor production of Grimms’ Fairy Tales and get eaten alive by midges (not included in the ticket price).

On the way there, we were stuck on the M25 for an hour-and-a-half. We were overtaken by a mobile refreshment van bearing the legend “Nice Buns”.

After the endless accelerate brake; accelerate, brake, as we crawled and stopped; crawled and stopped, I developed agonising cramp in my right foot and had to drive off the motorway, stop in the nearest car park and walk it off. The reserve driver had to take over.

The next day dawned hot and Oxford was heaving with guided tourists who were clumped at each corner taking pictures of each other. Having folded away my waterproofs and thermal vest, I went out in a strappy top only to realise while riffling through the clothes on the sale rails that I had omitted to shave my right armpit. The left, silky smooth; the right, bristly as a worn scrubbing brush.

Bet this never happened to Angelina Jolie.

Immediately, I clamped my right arm tight to my side. No one shows underarm stubble in Karen Millen. I could still use the arm as long as it moved only from the elbow down, like a robot. Meanwhile, I carried out more extravagant moves with the other arm despite having a desperately unco-ordinated left side.

It wasn’t too bad until I went into Caffe Nero in Blackwells bookshop where, with my new book (not That one) in one hand, I needed to pay and then pick up my cup of coffee – all without showing my right armpit. In the end I gave up and decided to be French on my right side and English on my left. Tres continental � droit; pas de tout Continental � gauche.

I can only assume it was that little bit of Frenchness that helped me overcome my English primness and impelled me to buy That Book.

English Lynne: “What do you need to buy that That Book for?”

French Lynne: “Ooh la la!”

English Lynne: “Do you actually know any French?”

French Lynne: “Un peu, actuellement. Donc, est-tu going to acheter Cette Livre?”

English Lynne: “Well, yes. But I’m going to pretend to be French.”

French Lynne: “Forgettez not to show la pit de le bras droit.”

I toughed it out, dear reader. I picked up an unthumbed copy of Fifty Shades of Grey, thumbed through it, gulped, rallied and went to the till to pay, stretching out my French right arm with pride (soigner). I took my copy boldly and even refused a bag for it.

So I have my first dirty book, unless you count the time I dropped my A-level poetry textbook in the mud.

Would it teach me anything I don’t know? After all, I’ve been married 34 years and I’ve seen all the Carry On films and I worked as a cinema usherette when they showed She Died with Her Boots On (and little else). Oh yes, I have lived.

I showed my husband my new paperback with my cover story ready (ie It’s for research purposes) but he didn’t look unduly worried and, in case you wondered, he is aware it isn’t a Dulux paint chart.

I am up to page 20. So far I have discovered that the Grey of the title is the protagonist in the story; not to be confused with the “gray” of his eyes and his suit.

But it’s just as well I’m writing this now because, if the rumours are true, by page 120 I will be trembling so much I will be unable to type another word.