Gordon Brown invoked the wartime spirit of Winston Churchill yesterday when he made a surprise pre-Christmas trip to the Afghanistan front line just hours after bombs killed four British troops in the area.He was flown to the top of Roshan Tower post, situated in the thick of the Helmand fighting zone – and, in so doing, out-machoed his predecessor Tony Blair, who never left the safety of a fortified British base. (edit)Downing Street aides claimed that no British Prime Minister had been as close to a major front line since Winston Churchill in the Second World War.(edit) But the...