Just why this letter of thanks, from July 1945, has only now been seen in public is unknown and now on display @ Bletchley Park Museum.

One excerpt:
I am very well aware of the immense amount of work and effort which has been involved in the production of the material with which you have supplied us. I fully realise also the numerous setbacks and difficulties with which you have had to contend and how you have always, by your supreme efforts, overcome them.
Thank you "Ike" anyway.