The British Eastern Telegraph Company arrived in Portugal to complete the telegraph lines between England and India. It purchased a property at Carcavelos, which was thought an ideal location being close to the ocean and to Lisbon. The Cable project reached completion in 1870.
In 1932, the beautiful palace in the property (1750's) was transformed into a school for the British children.
When World War Two broke out many people fled to Portugal, the majority of whom were in transit waiting to go to America. A direct result of this was that the school housed 17 different nationalities, making it a truly international school. The strategic placement of the Cable & Wireless Company meant that many British Armed Forces messages were being relayed through Carcavelos. It was just a matter of time until German spies started to decode messages transmitted from Carcavelos to England. Using an old building just outside the company grounds as a base, they tunneled to the cables and intercepted the signals leaving Carcavelos. (St. Julian's School)
I believe this was the building used by the Germans.