Army bands have a history that dates back hundreds of years and the Ministry of Defence is still Britain's largest employer of musicians. These skilled instrumentalists are involved in some of the country's great ceremonial events but they are also fully trained soldiers with a key wartime role. In a year which has seen military bandsmen and women take centre stage in the Jubilee, Petroc Trelawny meets new recruits and veterans of many a Trooping the Colour. And just how do you play the euphonium while on horseback?