The suspect accused of attempting to assassinate Donald Trump last month at a gala in Washington DC has pleaded not guilty to all charges. Cole Tomas Allen did not speak in court on Monday as his attorney entered the plea on his behalf. The charges against him include attempted assassination of the president, assault on a federal officer and firearms offenses. The first charge carries a potential sentence of up to life in prison. Prosecutors have accused Allen of firing a shotgun at a US Secret Service agent and storming a security checkpoint in a foiled attack at the annual White House correspondents’ dinner, where Trump had gathered with senior administration officials, and more than 2,500 members of the Washington press corps. The suspect is alleged to have traveled by train from California to Chicago and then on to Washington, where he checked in as a guest at the Washington Hilton, where the glitzy annual gala was held on 25 April.…