Not strictly true, but when our boys/girls in blue do carry, they don't mess around: the police at Heathrow (the only place they routinely carry; every force has an ARU) are armed with sub-machine guns.
[link|http://image.guardian.co.uk/sys-images/Guardian/Pix/pictures/2004/01/02/heathrow.jpg|http://image.guardia...1/02/heathrow.jpg]