By David Milliken and Martin Quin Pollard LONDON/BEIJING (Reuters) -The BBC said Chinese police had assaulted one of its journalists covering a protest in the commercial hub of Shanghai and detained him for several hours, drawing criticism from Britain’s government, which described his detention as “shocking”. China disputed the account and said the journalist had not identified himself as a reporter. “The BBC is extremely concerned about the treatment of our journalist Ed Lawrence, who was arrested and handcuffed while covering the protests in Shanghai,” the British public service broadcaster…