By Zara Woodcock Celebrity chef James Martin and his girlfriend Louise Davies have split up after 12 years together. The 51-year-old chef and the TV producer started dating in 2011 after meeting on the Celebrity Who Wants To Be A Millionaire? set. However, according to a spokesperson, the duo made the decision to go their separate ways back in December last year. The two still remain friends. News of their split comes after he was pictured looking at watches in Mayfair, London, with personal trainer Kim Johnson. She was formerly married to businessman Arun Nayar – who was once also married to …