LONDON (Reuters) – Multi-millionaire art collector Charles Saatchi said on Sunday he would divorce celebrity chef Nigella Lawson, citing his "disappointment" that she had not defended him after photographs of him grabbing her neck during a row caused a public outcry. Lawson, 53, is hugely popular in Britain for her television cooking shows, which she presents in her trademark flirtatious manner, and line of cookbooks. She is also widely known in the United States, Australia and other English-speaking countries. …