Radical Islamist Anjem Choudary is reported to have featured in a video that threatened UK Muslims, according to the Daily Telegraph.
Mr Choudary allegedly called David Cameron and Home Secretary Theresa May "pathetic foolish leaders".
The preacher told the newspaper: “I am happy for what I say anywhere in the world in any clip because at the end of the day I believe that I speak what is right according the divine texts.
“If they want to use that clip I don’t have any problem with that at all.”
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Mladic, now 75, was the military commander of Bosnian Serb forces in the 1990s, who fought against the Bosnian Croat and Bosniak armies.
Weather: Heavy rain and strong winds in the north
His representatives said Cassidy, who was hospitalised last week, died "surrounded by those he loved."