Mr Pu, well known for his work defending freedom of speech, was arrested in June and has sometimes been subject, says his wife Meng Qun, to interrogation sessions that last up to ten hours. She wrote, in an open letter to President Xi Jinping: 'Even a young and vigorous healthy person would not be able to stand it. He has been subject to inhuman mental and physical torment...I believe in his innocence...Please be merciful and let my husband come home.' Source: Daily Mail