 Crichton, Michael (qv) based his book and movie only loosely on  the actual crime committed in 1855. In real life there were four  criminals: Pierce, Agar, the railway guard Burgess, and a railway  clerk named Tester. All four keys were kept on railway premises, two  in London and two in Folkestone. They were stolen temporarily by  Tester and Pierce respectively so that Agar could duplicate them,  but it turned out that the Folkestone keys were not being used  anyway. The guards van was not locked from the outside; Pierce and  Agar were let in by Burgess, and a share of the loot was handed out  to Tester, at stations. None of the criminals was spotted at once;  it was months before the railway conceded that the crime must have  occurred on the train. The details came to light after Agar had been  convicted in an unrelated crime and his accomplices decided to steal  his share instead of using it, as he had asked, to provide his  mistress an income. She got word to him, and he turned Queens  Evidence against the others, and told all. At no point in the case  did anyone escape from custody.