Chugalug2 & Franek - Re Polish Codebreakers
A long but informative Wiki article here:
https://en.wikipedia.org/wiki/Biuro_Szyfr%C3%B3w
Marian Rejewski and Henryk Zygalski hiked over the Pyrenees with a guide (who robbed them at gunpoint) to the Spanish border, where they were arrested on January 30, 1943.[77] They were incarcerated by the Spaniards for three months before being released, upon Red Cross intervention, on 4 May 1943.[78] They then managed, by a circuitous land–sea–air route, to join the Polish Armed Forces in Britain,[79] Rejewski and Zygalski were inducted into the Polish Army as privates (they would eventually be promoted to lieutenant) and put to work breaking German SS and SD hand ciphers at a Polish signals facility in Boxmoor. Because of their having been in occupied France, the British considered it too risky to invite them to work at Bletchley Park
[from Kozaczuk, Wladyslaw (1984), Enigma: How the German Machine Cipher was Broken, and How it was Read by the Allies in World War Two, edited and translated by Christopher Kasparek, Frederick, Maryland: University Publications of America, ISBN 978-0-89093-547-7 A revised and augmented translation of W kregu enigmy, Warsaw, Ksiazka i Wiedza, 1979, supplemented with appendices by Marian Rejewski]
FWIW Boxmoor is near Hemel Hempstead in Hertfordshire.
WT