The three major Birmingham GPO factories that I worked at were the Jubilee Works in Sherlock Street,  Fordrough Lane in Bordesley Green and Garrison Lane .

Here I worked on many components for the GPO Telephone network mostly very boring but they did include the HANDEL Nuclear Attack Warning equipment known as Wire Broadcast System WB400. and equipment for Regional Seats of Government or RSGs which were part of Britain's civil defence preparations against nuclear war

This was an interesting place to work especially during the The Cuban Missile Crisis of October 1962. The constant beep from the WB400 system concentrated our thoughts.

I did not know until much later that in the 1940s some components for Colossus Computer were constructed in the Garrison Lane factory.

Colossus was the world's first fixed program, digital, electronic, computer an electronic digital computer. Its primary function was to decode messages from the German Lorenz SZ-40 cipher machine that was used by the German High Command.