Bletchley Park is an excellent day trip from London. The train takes about fifty minutes from London Euston and then it is a short walk from Bletchley station to Bletchley Park. I spent about five hours there and still didn’t see everything. What I did see, though, was truly fascinating. The impact the codebreakers had on WW2 and on the modern computer age is very clearly explained. The place is well organized and the staff are knowledgeable and enthusiastic. Definitely worth a visit.