Re-enacting battles from World War Two is a popular summer pastime in the UK, but although we won the war it's the Germans that most people want to portray and the 'SS' who are the most popular of all. John Sweeney tours the biggest event of its type in Kent and discovers a darker side to the fun, with a convicted holocaust denier signing books, a trader selling a relic from Belsen, and some Nazi enthusiasts expressing extreme racist views.