Complex sentence: The comedian never identified himself as the person in the picture, but had an acquaintance with the British painter, George Clint, who claimed the picture as his own until the National Portrait Gallery of London examined it in 1914.
Split into simpler sentences: The comedian never identified himself as the person in the picture, but had an acquaintance with the British painter, George Clint. He claimed the picture as his own until the National Portrait Gallery of London examined it in 1914.