Telecoms at Bletchley Park
Photo: Bletchley Park mansion and grounds © LSA August 2015.

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In the 1940s the covert activities at Bletchley Park were said to have shortened the war by several years as well as forming the foundations of modern communications.

Now, in the 21st century, by combining old and new technologies to revive long-forgotten memories and neglected buildings, the electro-mechanical machines of the 1940s are being replicated so that the fascinating story of the code-breakers and early computing pioneers can be told. The Park is still a sprawling site, with lots of unobtrusive single storey huts and buildings seemingly of little importance, which have survived since World War II, and these are gradually being brought back to life, as funding permits.

Bletchley Park has many connections with telecommunications that have set the standards for the way we communicate today. Post-war, training courses at the Park included Civil Aviation, Teachers' Training, Post Office clerks and engineers of all grades, making the site key to the evolving technology and social world of the Sixties and Seventies. Here we attempt to unravel just some of the Government and General Post Office (GPO) history associated with the Park.

As a Government site, the activities at the Park were always subjected to some secrecy, even after the war, so it's not easy to track the many changes over the years as departments re-organised and relocated. These pages are subject to revision as research uncovers additional information, and more stories can be told...


The Government & Cypher School moved into The Park in 1939 and vacated circa 1946. The Post Office Training Schools were established circa 1947 and as BT did not finally vacate the site until 1993, then the telecommunications timespan is much longer!

  • 1939 - GPO history begins as the all important telephone lines were installed into the Park.
  • 1943 - The first prototype Colossus was working at Bletchley.
  • 1946 - All traces of Colossus were removed from the Park.
  • 1947 - The GPO training schools moved into Bletchley.
  • 1993 - The GPO (British Telecom) moved out of the Park.
  • 1993 - The Colossus rebuild began using GPO components.
  • 1996 - 6th June Colossus rebuild was switched on by HRH The Duke of Kent.
  • 2000 - Colossus Mark 1 was almost complete.
  • 2007 - Bombe Rebuild switch-on.
  • 2011 - Tunny Rebuild completed.
A Study of the Park  
A Study of the Park
Follow the progress of restoration at the Park, as funding and policy have changed over the years to make it the living story of wartime code-breaking...

Photo: The Park © LSA August 2015.
The GPO at Bletchley Park  
Telecoms at Bletchley Park
Bletchley Park has many connections with telecommunications that have set the standards for the way we communicate today. These pages will look at just some of the General Post Office (GPO) and Government history associated with the Park.

Photo: An original uniselector which was used in Colossus © LSA July 2007.
The National Museum of Computing
Marvel at the Mainframe computers of not so very long ago... and many other exhibits.

Photo: Disc drives and equipment of the ICL 2966 © LSA June 2012.
The Colossus Rebuild  
The Colossus Rebuild
From 2012, Colossus is displayed in a new gallery, so you can more easily admire the fantastic achievement of the rebuild.

Photo: Close up on Colossus. Note the Light Straw coloured relay cans which would all have been Battleship Grey on the original © LSA July 2007.
The Bombe Rebuild  
The Bombe Rebuild
On 17th July 2007, to coincide with the 50th Anniversary of the British Computer Society, the Bombe Rebuild was switched on after 12 years of meticulous reconstruction. The exhibition and display in B Block provides a detailed insight into the mechanics of code breaking.

Photo: Bombe Rebuild © LSA July 2007.
The Tunny Gallery  
The Tunny Gallery
The Tunny Rebuild gallery was opened on 26th May 2011...

Photo: Tunny Gallery © LSA June 2012.
Further Info  
Further Info
Web links, books and videos complete the story...

This site is dedicated to Margaret Davies who, during the war, worked on a lathe at BTM Letchworth, making components for the Bombes.
Design, images and text compiled by © Light-Straw. Page last updated August 2015 revision.

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