Superintendent Richard Moore of Birmingham Central Police said the fatal stabbing of two men in Birmingham city centre was a "dreadful" and "exceptionally rare" incident.
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Hundreds hit the streets of some of England and Scotland's biggest cities in protest over the "anti-immigration" tone of the Brexit campaign
Michael Fallon has received reassurances from his US counterpart that security ties with Britain will "endure" following a vote for Brexit.
The showers will be slow-moving, heavy and thundery at times, particularly in central and eastern areas.