One could be forgiven for imagining 1920s Horsham to have been untouched by the parties and scandal taking place in the capital. But one would be wrong, because Horsham too was roaring.

“A little old lady told me she remembered seeing naked ladies running around shrieking and leaping in and out of a swimming pool at a house in The Needles,” says Jeremy Knight, Horsham Museum’s personable curator.

“I thought she must be mistaken but I did some research and it turned out a Hollywood film producer lived there and used to hold wild soirees.”

It’s just one of the stories to have surfaced as the museum mounts an exhibition of fashion from the period. Interest in the early part of the 20th century is at a high thanks to what Knight calls “the Downton effect” after the phenomenally successful Sunday night costume drama Downton Abbey, which sees Dame Maggie Smith and Hugh Bonneville slink around country piles in fabulous outfits.

Never one to miss an opportunity (last year they capitalised on the Doctor Who anniversary with an exhibition on local Dalek designer Raymond Cusick), the museum has opened up its archives to showcase everything from maids’ uniforms to dazzling cocktail dresses.

Sniping about the TV show’s perceived historical inaccuracies is a favourite pursuit for certain viewers but Knight noticed that costume was one area that never came under fire, something he attributes to the skill of the award-winning costume designers who will spend months picking through museum archives for research.

The attention to detail even extends to garments used only for set-dressing.

At one auction, Knight met a researcher for the show who had just snapped up a bundle of superfluous vintage underwear from Horsham Museum to use in characters’ bedrooms.

“Designers spend a lot of time raiding museum archives but the public doesn’t often get that opportunity,” he says.

“We thought it would be nice to give them the same access.”

Each of the exhibits was donated to the museum by local people, much of it in the 1950s and ’60s, and is mainly in pristine condition.

“The wonderful thing about the early to mid-20th century is you’re dealing with a period where people kept things. Garments such as a cocktail dress would have been worn for a few years until they went out of fashion then stored away somewhere until, eventually, they find their way to us.”

Sadly, the details of the people who once owned the clothes have not enjoyed such longevity. “We often know more about clothing from the 1840s than more recent items. We know quite a lot about the owner of a Quaker wedding dress in our collections but others are a mystery. That can be quite appealing – you have to imagine who wore it and where.”

Downright Downton opens another fascinating and diverse year at the popular museum. A “memories and memorabilia” exhibition on the First World War marks this year’s centenary, and includes everything from trench periscopes to early Valentines’ cards, copies of front line satirical magazine The Wipers Times and a uniform worn by celebrated war poet (and former Christ’s Hospital school pupil) Edmund Blunden.

This will be followed by an exhibition on collectors of the weird and wonderful, before a summer show that looks at the infamous Horsham dragon, apparently encountered in the town 400 years ago and reported in a newspaper of the time as a 9ft-long beast that killed two people and left a trail of posionous slime behind it.

“We think now it was just a giant serpent,”

says Knight, not entirely reassuringly.

*Downright Downton runs until May 2014.

Visit www.horsham museum.org for full details