FROM the front, it has to be said, not much has changed at York Art Gallery, which reopens on Saturday after an £8m development. Its grand Victorian façade stands proudly on Exhibition Square and a statue of the city’s most famous artist son, William Etty, looks a little brighter after recent conservation.

But inside, and to the rear, it's a different story. As soon as you step through the front doors you are greeted with a fantastic view of the original roof space, which had been hidden away for more than 50 years. It now towers above a new mezzanine level which has been built like a giant table structure above what was known as the main gallery.

The roof void was something Dr Janet Barnes, CBE, chief executive of York Museums Trust, had her eyes on ever since she took the role in 2002. “Most visitors to the gallery over the last few decades would have had no idea that this spectacular space was hidden away above their heads. In the 1950s the opaque glass ceiling was put in to help control the environmental conditions needed to show paintings, meaning the fantastic Victorian architecture was locked away behind a little hatch. I was as taken aback as anyone when I first saw it,” she says.

Since 2002, the trust has invested in the gallery and its other sites – York Castle Museum, York Museum Gardens and the Yorkshire Museum – with a series of renovations, developments and major exhibitions, but the “Secret Gallery” was never far from Janet’s thoughts.

“As soon as I saw it I knew we needed to open it up once more and I showed everyone who visited. But for a project that size you need a lot of money,” she explains.

It wasn’t until 2011 that the idea for opening up the space became a possibility. Unknown to the gallery Karen Madsen and her brother, Peter, had retired to York and were interested in art and archaeology and when Karen died, she generously left £300,000 to the trust. Peter Madsen was a regular visitor to the gallery, and quietly enjoyed the art on show. When he died a year later he left his estate to the trust, which also included the residue of Karen’s estate. In total, the amount they jointly left was £2.2m, a game-changing amount which enabled Janet to think that a major transformation of the gallery could be possible.

“This whole project would not have been possible without the generosity of Peter and Karen Madsen. Their estate was the seed money that enabled us to explore whether such a project was feasible and allowed us to bid successfully for further capital needed to carry out a project of this size. We are extremely grateful and have named the new suite of three galleries on the ground floor The Madsen Galleries in their honour,” she says.

The gallery shut on December 31 2012 for the development to take place. As well as the new mezzanine gallery, the archives, which were previously housed in the northern ground floor area of the building, moved to Explore, York’s main library. This enabled the creation of a symmetrical suite of three galleries on the ground floor. This, combined with the mezzanine and a new first floor gallery on the south of the building means there is 60 per cent more exhibition space.

“This increase in space allows us to showcase even more of our nationally designated collections as well as giving us the space and conditions needed to attract much larger touring exhibitions in the future which previously would not have been possible,” says Janet.

Walking around among the Italian Old Masters, the Hockney, the Turner, the Lowry paintings, it makes clear the breadth and quality of the gallery’s collection. This has been enriched for the opening displays with loans from national galleries and thought-provoking new commissions. Susie MacMurray’s Halo, shimmers on a distant wall, barely visible at times. It is only when you get close do you see the thousands of gold plated wire loops used to create a magical piece which alludes to the gold work in the masterpieces hung nearby.

Another new work is Clare Twomey’s Manifest: ten thousand hours. With the help of York students and many volunteers she has made 10,000 slipcast ceramic bowls, now piled in towering columns. The precarious nature of the stacked works alludes both to how collections grow and the challenges this presents to collectors, and to the idea that it takes 10,000 hours of practice to become a master craftsman.

This is the centrepiece to the new Centre of Ceramic Art (CoCA) which will showcase some of the 5,500 examples of the gallery’s British Studio Ceramics collection, the largest in the country.

Almost 2,000 ceramic works will be on display as part of CoCA, including star pieces by key makers including Grayson Perry, Bernard Leach, Edmund de Waal, William Staite Murray, Felicity Aylieff, Lucie Rie, Hans Coper and Kate Malone.

From CoCA a first floor balcony looks over what will become a new Artists’ Garden and an Edible Woodland. This previously hidden corner, surrounded by the Abbey’s mediaeval walls, link York Museum Gardens to Exhibition Square, via new green pathways with places to sit and take in the sun and enjoy this new public space. There is a new Garden Entrance of the gallery which will lead visitors directly from the displays of art to an oasis of calm.

* Opening hours: Sat 10am to 8pm, Sun Noon to 4pm, Mon to Fri 10am to 5pm. Tickets: 12-months YMT card £22. Day tickets adults £7.50, children 16 and under (free with paying adult up to a limit of four). See website for concessions yorkartgallery.org.uk

Tel: 01904-687687