<p><br /> Police have risked controversy as they "kettled" several hundred protesters after clashes during student tuition fee protests.<br /> </p><p><br /> Demonstrators were penned in by riot squad officers in Whitehall after a stranded police van was attacked and vandalised.<br /> </p><p><br /> Scotland Yard said it would bring in portable toilets and water but said it was unclear how long people would have to remain.<br /> </p><p><br /> The tactic, which police call "containment", was heavily criticised after up to 5,000 people were held during G20 protests in April last year.<br /> </p><p><br /> Denis O'Connor, HM Inspector of Constabulary, said the move carries risks, particularly if vulnerable people are caught up inside.<br /> </p><p><br /> Hundreds of people chanted "let us out" as a line of police officers reduced the size of the Whitehall pen.<br /> </p><p><br /> The demonstration followed a day of action two weeks ago that saw 60 arrested and dozens injured when a riot broke out at the Conservative Party headquarters.<br /> </p><p><br /> Marches have been held across England and Wales, with school and college students joining the action.<br /> </p><p><br /> Cities including London, Birmingham and Manchester were holding rallies, with university workers protesting alongside students.<br /> </p>
