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 prominent Brexiteer says leaving the bloc will offer a "once in a lifetime" opportunity to set reform environment policies.
The Severn Crossing tolls will be abolished next year, the government has said. Currently cars are charged £6.70 for a return journey.
An Australian bride-to-be shot dead by a US officer after calling 911 "should not" have been killed, say police.