Eminem was banned from playing London's Hyde Park because of his "offensive" and "unsuitable" lyrics according to documents.
The 'Rap God' MC, who has announced two dates at Wembley Stadium next month instead, tried to get London mayor Boris Johnson to overturn the decision to stop him from performing at Barclaycard British Summer Time - but his staff admitted they didn't know who the rapper was.
The comments feature in a number of letters and emails revealed following a Freedom of Information request by the Daily Mirror newspaper.
Royal Parks, which runs Hyde Park, claimed the show would "upset" other park users and promoters AEG had the decision referred to Boris Johnson.
His chief of staff, Sir Edward Lister, said: "Until receipt of both emails I had no knowledge of Eminem and his style of music and still do not."
They decided it was down to Royal Parks to make the decision and the star was banned from performing.
In an email, Royal Parks CEO Linda Lennon said: "This artist flagged risks across the board. In particular in respect of our public reputation.
"The nature of any act with potential for lyrics to be deemed offensive and/or unsuitable language being audible within the park as a whole, let alone the surrounding residential areas, is unacceptable."
Eminem, 41, will now play two sold-out shows at Wembley on July 11 and 12 and admitted it upset him when he was told he couldn't play Hyde Park.
He said: "That's mean, man. It kinda hurt my feelings.
"The easiest way to get me to do something is to tell me I can't do it. Thanks to the Royal Parks for making it all possible ... for Wembley."
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