What was amusing was that they went out and got legal opinions on stealing the design. It was agreed that there was a patent (3 in fact) and that, in normal business, they should licence it. Given the circumstances (even in '34) they invoked a rather obscure right to use it without asking "in the National Interest" "but accept they would have to pay a licencing fee when secrecy was no longer required".
I wonder if they ever paid up?
I presume that if the Germans did think the Brits were using Enigma machines they didn't bother to try and crack them as they knew they were "unbreakable"