Liberal Democrats' spring conference

Demonstrators outside Sheffield City Hall Photograph: Owen Humphreys/PA

A police officer prepares riot helmets as demonstrators gather outside Sheffield City Hall, where the Liberal Democrats' spring conference is taking place. The conference centre is surrounded by a ring of steel fencing as demonstrators vent their objections to the party policies the Lib Dems have agreed to in government but had opposed before the 2010 election Photograph: Christopher Furlong/Getty Images

Deputy prime minister Nick Clegg chats to youngsters in a cookery class during a visit to the Vox Centre at Hillsborough Stadium Photograph: Anna Gowthorpe/PA

Students demonstrate in Sheffield outside the Liberal Democrats' spring conference Photograph: Owen Humphreys/PA

Business secretary Vince Cable during a question-and-answer session Photograph: Nigel Roddis/Reuters

Demonstrators behind the ring of steel Photograph: Christopher Furlong/Getty Images

A delegate looks on as demonstrators gather outside Sheffield City Hall Photograph: Christopher Furlong/Getty Images

Demonstrators outside Sheffield City Hall Photograph: Owen Humphreys/PA

Deputy prime minister Nick Clegg speaks during a question-and-answer session at the Liberal Democrat spring conference at the City Hall Photograph: Anna Gowthorpe/PA

Demonstrators gather outside Sheffield City Hall Photograph: Christopher Furlong/Getty Images