The UKIP leader Nigel Farage has said:
Since I first met Sir Patrick when he dominated a UKIP stage in 1999, he has been a friend and an inspiration. Not only to us in UKIP, but across the country and around the world.
Today we have seen the passing of a true great, and a true Englishman.
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Political parties across the country suspended their General Election campaigns following the Manchester Arena terror attack on Monday.
Investigators believe Mr Kushner has significant information relevant to their inquiry, officials told NBC News.
The men were detained as part of an investigation by MI5 and the Metropolitan Police's Counter Terrorism Command.