Patrick Rock was so senior an aide to U.K. Prime Minister David Cameron that he was one of only three who had an office in No. 10 Downing Street, the prime minister’s official workplace. One of the main things he did there was to oversee government policy on the firms that create internet filters to combat child pornography. So by the laws of ultimate irony, Rock was arrested on suspicion of offenses related to child porn, The Telegraph reports. Rock’s computers at Downing Street have been investigated, but it hasn’t been reported what they did or did not find. Rock, for his part, resigned one day before he was arrested last month.