"We would only want this to happen for drugs we're confident are safe," Health Secretary Jeremy Hunt said of a new "fast track" scheme to allow severely ill people access to drugs not yet on the market
He said people diagnosed with serious illnesses "very often want to volunteer" to take part in clinical trials, adding that he wants the UK to have the world's "biggest bank" of volunteers willing to take part in such trials.
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The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.
As temperatures climb through the day, the warmest spots are likely to be across western parts of Northern Ireland and western Scotland.
Boris Johnson and Amber Rudd have both criticised social media giants for failing to detect and remove extremist material online.