There is understood to be a 100m cordon in place around Grand Arcade in Cambridge following reports of a suspicious package.
Bomb disposal teams have been dispatched, police are expected to be in the area for several hours.
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Ukip has responded to the resignation of its only MP, Douglas Carswell, by suggesting he quit before he was kicked out.
A mostly warm afternoon but a fresh easterly breeze will bring a noticeably cooler feel along eastern coasts. Highs of 15 deg C (59 deg F).
ITV News Anglia's Political Correspondent Emma Hutchinson asks what next for UKIP after Douglas Carswell quits the party?