Rosemary Hawthorne knows better than most the peculiar quirks of the British. At one point in her show on the history of underwear she does nothing more than silently pull an enormous pair of bloomers from a case. The instant guffawing from the audience speaks volumes about the show’s ongoing appeal.

A RADA-trained actress and wife of a vicar (now retired), Hawthorne’s fascination with what she calls “our hidden history” has turned her into The Knicker Lady, a woman who tours the country with a trunk containing four centuries’ worth of smalls (and indeed, not-so-smalls). It’s a monicker somewhat at odds with the 74-year-old’s RP vowels but she’s not complaining.

While they might seem trivial garments, Hawthorne believes what we wear under our clothes is just as interesting as what we display to the world.

Aside from the curious element of paradox – the tweedy women who sidle up after shows to assure her they are “seductive underneath” – underwear presents a unique form of social history, from the knitted knickers of rationed Britain during the Second World War, through the throwaway paper pants of the sexually liberated 1960s to the infamous thongs of today.

It’s a particularly colourful area and one of the highlights of performing the show is the stories it brings out from the audience. There is usually an abundance of humorous episodes involving slack knicker elastic and dancefloor disasters, mixed in with romantic recollections of wedding trousseaus, and vignettes from past times when modesty dictated that people hung their washed underwear out to dry shrouded in pillow cases.

Hawthorne didn’t start out beneath the petticoats, she laughs. Her time as an actress had ended abruptly when she married and had seven children or, as she puts it, “Sarah Bernhardt became Mother Earth”.

In his 40s, her ad-man husband “switched his collar around” to become a vicar and, deciding she needed to bring in some extra income, Hawthorne began buying and trading in vintage and antique clothing. Initially she focused on conventional items – dresses, shoes, scarves.

Then a friend who ran an antiques stall insisted she add a pair of Victorian knickers to her collections and she was hooked.

Today she is the author of The Costume Collector’s Companion, as well as three books on the history of underwear– including Knickers; An Intimate Appraisal and Bras; A Private View.

Her collections take up most of the attic in the couple’s terraced house in Devizes, Wiltshire. “I was just thinking about pressing my draws when you called,”

she says playfully.

Hawthorne insists she is not a hoarder, yet will admit they had to hold a contents sale when they moved out of a previous home, and says she once moved into a house unconcerned about whether the children would have to share rooms but fretting about where her collections would be stored.

Many items are donated to her, often anonymously, others she tracks down in markets, auctions and charity shops.

“First of all I l look to check it’s genuine – there are a lot of things made for re-enactment and fancy dress now – but beyond that I’m looking to see if it says anything to me. I rarely know who something belonged to but I love imagining.”

The actress in her can’t help seeing clothes as a character study, she explains.

“Handbags in particular tell you so much about the owner, as do suits and dresses – the worn pocket where someone always stuffed a hanky; the seam that’s been let out to accommodate weight gain.”

Hawthorne’s fascination with clothing began early – even at the age of four she remembers twirling in front of a mirror in a red coat her mother had made for her, whispering “I’m Red Rosemary” to her reflection.

In the school holidays she would go to the London fashion house where her mother worked as a personal secretary to help dress the models. “I realised even then that clothes had dual purposes. There were the tweed suits and winter coats bought for practicality, and the dresses and cruise wear bought for pleasure.”

These days she worries the balance has shifted too far towards frivolity.

“People buy clothes they don’t need on a whim then chuck them out a few months later. We’re like lemmings, blindly following the latest bit of marketing – totally proliferate. My mother’s generation kept things and took care of them. My generation sewed our own clothes and altered patterns – it was creative. Today we’re just in a rush to get more and newer.”

Yet the ongoing popularity of ‘vintage’ suggests there is an appreciation of the quality and craftsmanship of the past.

“I think people like vintage because it smacks of a nicer world – easier, steadier.

Although that’s looking at the past with rosetinted spectacles, I can understand that nostalgia.

The romantic element of me really likes the 18th century but I wouldn’t want to live there.”

And sewing is seemingly making a comeback, judging by shows such as BBC Two’s The Great British Sewing Bee, a spin-off of the popular baking programme, which sees amateur dressmakers compete to be named the country’s best.

Hawthorne is delighted to be making several appearances in the series.

I wonder how her work has influenced her own choices when it comes to clothing – is she particularly conscious about the messages her outfits are sending out?

“I think clothes are important – of course – but I hope I don’t get too hung up on them. I certainly don’t fret about what I’m wearing.”

Her own style was described by one of her sons as “Little Grey Rabbit” – a practical, homely look formed during her years running around after numerous small children. Yet to this day she has never owned a pair of trousers. “I just prefer skirts and dresses. Partly I like to look feminine but I think also it’s a leaning towards earlier generations. I think we’re all fascinated by the past.

We love to look at old clothes because we want to know what we looked like then and who we were.”

*Rosemary Hawthorne brings The Knicker Lady to the Connaught Theatre, Worthing, on Saturday, Feb 22 at 2pm Saturday, February 15, 2014 5 and 7.30pm. To book, visit www.worthing theatres.co.uk