Secret War in Portugal [1939-1945]
For SOE [British Special Operation Executive] 24 Land was the code name for Portugal

The Lisbon Route

I bought it two weeks ago. No time to read it fully. It is not a book about MI9 ways of escape. It's a portrait of the «transformation of Portugal's tranquil port city into the great escape hatch of Nazi Europe.The author, Ronald Weber, is professor emeritus of American studies at the University of Notre Dame. 
More than a vivid report about the "spy's nest" that Portugal became, it's an academic work written as a fiction book, appealing the reader, in a way it's a primary source book about major events occurred in this country during WW2 concerning secret war in the frame of our neutrality. 
Published by Ivan R. Dee, Plymouth, UK, in 2011, ISBN 978-1-56663-876-0