Piers Morgan knew about illegal phone hacking when he was editor of the Daily Mirror, it has been alleged at the high court. The first day of the phone-hacking trial initiated by Prince Harry and other well-known figures heard claims that illegal activity, including voicemail interception, was “carried out on an industrial scale” by staff at Mirror newspapers. David Sherborne, the barrister acting for Harry and the other alleged victims, told the court that Morgan “must have known” about illegal behaviour at the newspaper he edited between 1995 and 2004. According to legal filings: In one alleged incident, Morgan asked…