How had evans planed his escaped?

Evans was a detainee in the Oxford Prison. He had tried to escape from the prison thrice and so in spite of not being a typical criminal, he was kept in that jail. People even gave him the name ‘Evans the Break” for that reason. Evan was a crafty and smart prisoner. He was always into some trick or the other to escape from prison. So people doubted his sincerity when Evans wanted to give an exam on O-Level German and get some academic qualification. Though skeptical, still they appointed a German teacher for him. He taught Evans for ten months. The Governor made the arrangements for his exam. But later, they realized that it was only a ploy of Evans for the fourth escape. He had made a master plan for that. After the completion of the exam, he impersonated the invigilator, Mc Leery. When the Governor came to check whether Evans was in his place or not, he found a bleeding Mc Leery who was bound in the chair Evans was sitting. He was taken to hospital. But later on the Governor got the news that no Mc Leery was admitted in the hospital, and that it was Evans who had deceived the Governor and escaped from his imprisonment. Soon after that the Governor finds some clue from the correction slip, given to Evans during the examination, about Evans’s hiding place. He catches Evans in the hotel but there the Governor did his last mistake. He neither took enough force to nab him at the hotel nor did he take the trouble of going with him in the prison van. Left all alone, Evans manages to make his final escape breaking all his handcuffs.