Light has a powerful way of influencing mood. It changes the way we interact with space. Shine a green light on a tree with red berries and it cancels them out; it looks like a different tree. Lighting helps persuade your mind to go down a certain route.

For me, cold white washes, such as standard office fluorescents, make a person feel worse. I've put lights in my bedroom that as best as possible match sunlight. Sit under that light for four hours and you do feel better. A cathedral lit in orangey sodium is sad. With white light it makes its presence felt. We lit Exeter cathedral in white and it changed the building itself. It's a clean light, more majestic.

You can tell how much light affects a person. Compare a dull, overcast day with a bright, sunny day. Darkness brings on a melancholic feeling, so why shouldn't we keep our lives nicely lit? Natural light is a good accompaniment to happiness. When it's two or three in the morning and the embers are glowing, you can't beat natural firelight. No artificial light comes close.

I like doing video projections - it's intensely fun - but it's not the same level of happiness I would find on a mountain or walking on Dartmoor with my partner. There's a strong distinction between happiness and fun. Projecting light at a massive New Year's Eve party is great fun but it's not happiness. Being in the natural world is happiness. Being happy without having so much fun is preferable to having fun but not being very happy.