I have done this kind of thing before, so I know the ropes. It gets easier each time but, rather like a penalty shoot-out, it’s impossible not to experience a twinge of panic.

I am gawping at row upon divine row of sensual lingerie: bras, knickers, basques, thongs, stockings, suspender belts and slinky garments of minimal construction, otherwise known as playsuits. I have no idea how the latter stay on – there are more holes than fabric – and I’m guessing they aren’t worn for creosoting the back fence.

The imagination wanders and a chap’s mind turns to how the sheer and lacy collections might look when worn, how they caress the flesh, the curves … It’s a red-blooded male’s idea of heaven – except it is also a kind of hell, because this delectable lingerie is in a shop, a shop staffed by women, who are looking at me, a bloke.

So what is a man like me doing in a ladies’ undies store? It’s Christmas, of course. It’s what we do at this time of year, buy lingerie for wives and girlfriends, even if the prospect scares the living daylights out of us.

Of course, it shouldn’t be a torment. After all, it’s only fabric and stitching, like socks really, just a smidgen more intimate.

Then there is the fact that purchasing bras and panties, let alone demure nurse outfits, is intrinsically linked with "IT", you know what, “extreme petting.” Oh, all right: sex. Buying stylish and attractive undies is tantamount to publicly declaring: “Yes, we enjoy an active sex life. Sometimes ,we’re a bit naughty. And we jolly well enjoy it, too.”

Then there is the fact that you don’t go to an alluring boudoir like Agent Provocateur at Birmingham’s Selfridges – which is where I am – if you have no interest in seeing the stuff worn. That’s what Marks & Spencer is for.

However, once you’ve got over the whole English reticence about hanky panky, choosing lingerie for the sunshine of your life is an absolute blast, one of the unsung joys of Christmas.

In a bid to demystify the whole business for our male readers, I agreed to head for the fourth floor of Selfridges to quiz Agent Provocateur’s assistant manager, Holly Fuller, about the do’s and don’ts of lingerie shopping for your sex goddess.

I quickly learn it is important to go with the flow, be confident, enjoy yourself. Don’t worry about being a lone man in a girls’ world. No-one will think you are a perv.

Holly makes the point that she and her assistants want to help men get great lingerie that “both parties can enjoy.” “That’s the thing about lingerie – it is for both of you,” says Holly. It’s the gift that keeps on giving.

“For us, lingerie is about feeling sexy and confident as a woman, whether you have got someone to show it off to or not. Obviously, if guys are buying it for their girlfriend or wife, something else comes into it.”

Like seeing it on, or possibly off.

One thing you will need to know, chaps, is your woman’s boob size. Have a

secret look at her favourite bra, the one she wears for special occasions, the one with the “wow” factor. Just don’t get caught peeking, unless that’s your thing.

Armed with cup-sizes and the like, the fun begins. Agent Provocateur has it all, from the sophisticated to the naughty. If sir thinks madam would like something classic, consider a French lace basque in the Love range (£185).

“It is a little bit more for a special occasion but it will give a lady very straight lines, especially if they are wearing stockings,” says Holly.

At the other end of the spectrum are the playsuits. The Cendrillon, which come in heat-sealed black lace, is a buttock-revealing joy.

“Doesn’t it chafe?” I asked Holly. “You’d be all right,” she says, “you” being the woman wearing it, not me.

There is a spanking black leather playsuit, with braces and hot-pant shorts, for £245. “That’s definitely for the bedroom,” says Holly. Or try the gold lame Britt if you like everything – and I mean everything – on show. There’s no hiding place.

Holly says such a purchase would probably be led by the woman. “Although a bloke might think he would want her to wear it, he probably would not go the extra step and buy it.”

So ladies, give him a nudge if it’s your bag. Just make sure the central heating’s turned up.

Suspender belts add an element of playfulness, according to Holly. “It is a little bit girlie. That French look,” she says.

If the love of your life prefers a less “in your face” approach – a slow burn, if you like – a babydoll is the answer and can be worn over a sexy set. “It is all about revealing – what you see and what you don’t see,” says Holly. Oh, la la.

Don’t ever be tempted to mix and match sets – which will look unintentionally cheap. The only exception to the rule is stockings, where a red or a pink, say, can add a splash of erotic colour to a black set of briefs.

Holly says: “If you have got a strong set of black lingerie, I would put a coloured stocking with it. She could wear red stockings and red lipstick. That is quite a nice thing to do.”

Stockings, I learn, are vital for the overall effect. Holly says: “If you are getting a suspender belt, you have to get stockings. Don’t assume she has stockings, or that she will want to wear her old ones with her beautiful new suspender.

“It is going to destroy the illusion if she has to go rooting around in her sock drawer. Don’t skimp on stockings. It isn’t worth it. It will destroy all your good work.”

As a final thought, consider the cut of the bra cup. As well as full, they come in demi and quarter, ideal for Christmas cleavage. Making the right choice will ensure your festive cup overfloweth, but not too much.