Episode 4

Inside every museum is a hidden world, and now, for the first time, cameras have been allowed behind the scenes at the world-famous Victoria and Albert Museum in London.

Only a small part of the two million wonders in the collection are on display to the public. But in this new series we go behind closed doors to explore all the treasures of art, design and performance the museum has to offer.

This week, we meet curators and conservators trying to preserve some of the finest examples of craftsmanship in the world.

Deep in the museum stores, curator Keith is trying to breathe life into an object of extraordinary craftmanship – an original Stormtrooper costume from the Star Wars sequel The Empire Strikes Back, from 1980. He's hoping to exhibit the costume in a refresh of the V&A's Theatre and Performance Display. But when he and conservator Susana unpack the moulded-plastic body parts, a key piece is missing – the Stormtrooper's helmet.

Unable to display the costume without the helmet, Keith contacts a group of prop-makers who specialise in making replicas of movie costumes. The prop-makers agree to make a replica of the original helmet, using the exact techniques pioneered by the Star Wars costume department in the 1970s. But the challenge for Keith's prop-makers is to turn this box-fresh helmet into an authentic match with the original decades-old costume.

Meanwhile, two of the largest galleries in the museum, the Cast Courts, are undergoing a renovation. These galleries are home to one of the world's largest collections of 19th century hand-made casts - replicas of some of Europe's finest sculptures. As few people then could afford the luxury of travel, art works could be brought to them with these painstaking replicas. Now it's the job of senior sculpture conservator Victor to give these precious casts a facelift.

The final part of the epic renovation is cleaning a piece representing the Assumption of the Virgin, made in 1890. This plaster cast depicts the Virgin Mary ascending to heaven surrounded by angels. It's a perfect plaster copy of one of a number of 14th-century sculptured panels made for the exterior of the Notre Dame cathedral in Paris. Now the plaster cast will be given its first deep clean since it was made 130 years ago.

The importance of these fragile replicas is brought into sharp focus with news of a terrible fire at Notre Dame. Although many artefacts are destroyed there is relief that the original cast of the Assumption of Virgin has been spared.

The news highlights the importance of preserving the V&A's delicate cast. But Victor and fellow conservator Adriana discover a crack in its structure, that could prove fatal. Over hours of careful conservation, the team work on supporting the fracture - but the real test will be when they try to hang it back on the gallery wall.

In the Rock and Pop archive, curator Vicky is examining a photograph donated after the V&A's David Bowie Exhibition. It's a rare print, known as ‘David Bowie is watching you', taken in 1973 as part of a series of photos by photographer Brian Duffy to become the album cover for Aladdin Sane. The picture was donated by the photographer's son Chris. Vicky wants to know more about the print and invites Chris to the museum. Chris remembers visiting the photoshoot when he was a teenager, and meeting David Bowie.

In paper conservation, senior preservations conservator Simon is dealing with a very different kind of photograph – a 65-metre-long Victorian photograph of the medieval Bayeux Tapestry. This unique photograph was commissioned by the British Government in 1871 and was one of the V&A's first interactive exhibits, displayed on a moving roller so audiences could spool through the panorama of the battle.

The last time it was on display was over 100 years ago. But years of manhandling have taken their toll. Now, the rolled-up photograph has been summoned to be part of a new V&A exhibition, filled with new images by legendary fashion photographer Tim Walker, inspired by objects from the museum's collection. But first conservator Simon needs to assess if the fragile piece is robust enough to be displayed again.

In the Rapid Response Department, curators Corinna and Johanna feel there is one important everyday object missing from their 20th-century collection. They have been offered a very British piece of graphic design – a road sign, made in 1961 by graphic designer Margaret Calvert. Before collecting the sign, they visit Margaret at her home, filled with familiar road signs…

We also follow fashion curator Oriole, who alongside colleague Susan, is on a mission to acquire a piece representing the best of contemporary British craft. They visit fashion designers Justin Thornton and Thea Bregazzi, known as Preen, at their workshop. Oriole and Susan have the difficult task of choosing one single piece to represent the designers.