"Metal seemed to provide the answer. I had previously worked on a building for a community centre in Gloucestershire that had a copper roof and knew that there would be the level of craftsmanship available to work with this material even given the complexity of the design. It's also a very long lasting material and is associated with buildings of importance like churches and civic structures. The Core represents the very heart of Eden - education - and so it seemed highly appropriate in that sense. Above all, copper looks absolutely beautiful and it will change colour over the years, eventually turning to a full green patina. But the chosen material needed to comply with the very highest of environmental and social requirements."

"Copper is not perceived by many as being particularly environmentally sound and our decision to use it in such a high profile way may raise a few eyebrows," explains Eden senior scientist Peter Whitbread-Abrutat. "But we all use copper every day and I see the Core's roof as a way of opening up the discussion on how best to mine, produce and use it responsibly.

"A number of options were open to us when it came to sourcing the copper. The first is the open market, but that would have delivered a mixture of copper from many mines around the world - some good and some not so." An obvious route would have been to go for recycled copper, which would cover everything on the sustainability checklist. Yet this was also dismissed. Peter explains: "We already deal with recycling as an issue at Eden. Surprisingly, only 40 per cent of the copper used in the world is recycled: because it is such a long lasting substance, most of the copper ever mined is still in use.