The Metropolitan Police has told ITV News that 50 people have been temporarily detained as a result of the 'critical mass' procession.
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The senior officials, including the head of leader Paul Nuttall's branch, condemned comments from him and millionaire backer Arron Banks.
Lukasz Pawlowski cut his throat with a kitchen knife as he was due to be sentenced in Havefordwest. He has been remanded in custody.
More than 1.85 million people have called for the US president's visit to be watered down to avoid causing "embarrassment" to the Queen.