- An estimated 300 Boxing Day hunts gather up and down the country despite the ban on hunting with dogs that was passed under Labour in 2005
- Campaigners say enforcing the restriction wastes police time, and suggest some officers turn a blind eye to breaches of the law
- But David Cameron has been accused of dragging his heels over acting on the coalition agreement promise of a free vote on overturning the ban
- Many Tories would support repeal, but most Labour and the Liberal Democrats are still in favour of the ban
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The threat level has been raised to critical by MI5's Counter-Terrorism Analysis Centre.
Prime Minister Theresa May announced the decision from Downing Street.
A man, apparently armed with a small axe and a large stick, was detained close to the event and police cleared the area as a precaution.