By her own admission, Dinah Collin often finds herself in some unusual situations.

Her work as a costume designer for stage and screen means one day might be spent immersed in the reserve collections of the British Museum, another sourcing the perfect 1930s suit for Bill Murray.

Recently she was tasked with bringing out the asexuality of the dragonflies in Glyndebourne’s The Cunning Little Vixen, which opened the opera house’s summer season.

It was director Melly Still who finally nailed it, deciding the singers should wear tights over their heads to blur their features. “Incredibly simple, but so effective. Of course, there was some sucking-in of breath when we first raised the idea but the cast were fine about it.”

In a popular production, critics have singled out Collin for her imaginative interpretation of writer Leos Janacek’s colourful cast of animals: the titular vixen, whose dreadlocks and chunky knits hint at her position on the outskirts of society; the gaggle of frou-frou hens – “Melly thought they should be sex workers” – and the mosquito, with his Sid Vicious look. “It’s a compliment to both Lucy Crowe [The Vixen] and costume designer Dinah Collin to say that you can practically smell the pair of them from the stalls,”

wrote Argus reviewer Eleanor Knight.

It is Collin’s first opera and living as she does, a stone’s throw from the opera house, her most convenient workplace yet. But her approach was much the same as for any of her projects, which include the 1995 TV adaptation of Pride And Prejudice, The Bourne Supremacy, Roman Polanski’s The Ghost and Nation at the National Theatre in London.

She compiled a series of mood boards taking in the characters, themes and emotions of the piece and batted about ideas with cast and director. She makes the process sound somewhat mysterious, but perhaps that’s because it is. “Melly felt the animals should have characteristics of animals but not be dressed as such,” she says. “With the humans, it just became clear they should be in black and white and the animals should be in colour.”

Collin has no formal training in costume design and admits she’s hopeless at pattern cutting and not much better at sewing. She originally studied illustration, which failed to excite her at all, and as soon as she graduated, she set about getting work in rep theatres, starting as a set painter and working her way up. In the late 1960s she was taken on as a costume designer by the BBC and the rest, as they say, is history.

Pride And Prejudice is one of the productions for which she continues to be best known – her designs for Colin Firth and co quite deservedly won her an Emmy.

It was a tricky project, she says, because of the lack of Regency period costume available to hire at that time.

Collin had to design and print appropriate fabrics herself and have costumes made from scratch.

She was keen to ensure the actors looked like real people wearing their own clothes, so spent a lot of time getting input from the cast. Darcy (Firth) was particularly interesting; his clothes needed to look authentic for the period while also appealing to modern audiences – it was important to emphasise Darcy’s masculinity and attractiveness. And how they did that. Firth’s Darcy is one of the best remembered of recent times.

Collin must therefore take some credit for him becoming the heart-throb he is today, I suggest. “Well, only slightly.

I think the make-up designer can take the real credit for that. She made him look amazing! He was quite sandy-haired and she made him look very dashing.”

If Collin is modest about her work, it is because she would rather it wasn’t noticed – or at least not immediately.

She is renowned for her “less is more” approach and her attention to detail. “The costume should be completely secondary so that you just become involved in the characters, particularly on television where it’s so important one believes in them. You know when you’ve cracked it because the actors are so appreciative. Lucy Crowe loves the way she looks as The Vixen in her cardigans and printed skirts and that sort of thing is so important to me because they are the ones creating these characters.”

Inspiration comes from all over – it’s obvious Collin’s mental reference library is vast, encompassing various historical periods, movements and continents.

For Nation, the National Theatre adaptation of the Terry Pratchett novel (also directed by Still), she describes afternoons lost in the British Museum.

“It’s set on a South Sea island at the turn of the 19th century, where a young Victorian girl is shipwrecked, but it’s a merging of all sorts of different cultures. I had no idea where to begin so I contacted the museum and went to look at all their objects and masks and clothes brought back by missionaries.” She pauses, presumably lost in the memory.

“It was extraordinary.”

The fabric for The Vixen’s costume was sourced by a contact in India who Collin met when working on The Bourne Supremacy in Goa.

She knew she wanted The Vixen to reference Roma gypsies and she wanted a fabric with “a flavour that is odd and different, something you wouldn’t associate with anything. India has so many prints – far more than ever make it over here – and when I sent her the pictures of my mood boards, she sent pictures of possible fabrics.”

Her work can next be seen in forthcoming film Hyde Park On Hudson, the story of the love affair between Franklin D Roosevelt (played by Bill Murray) and his distant cousin (Laura Linney) that centres on the weekend in 1939 when our King and Queen visited New York.

“With those sort of period films, it’s about taking original clothes and copying them. I wasn’t aware how many amazing late-1930s dresses there are sitting in New York costume houses.”

But I’m distracted by the cast. How wonderful, I say, working with Bill Murray. “Oh, he’s absolutely charming, a lovely man.

I actually brought him to Glyndebourne just before we finished the film. He came to see Turn Of The Screw and loved it. Then we got on the train and went to The Ram Inn at Firle for lunch – they couldn’t believe their eyes!”

* The Cunning Little Vixen is at Glyndebourne until Thursday, June 28. For tickets or more information, visit www.glyndebourne.com or call 01273 813813