John Gallehawk






How the Ultra Secret was nearly revealed by John Gallehawk

Bletchley Park Report No. 10 Published January 2011








Some Polish Contributions in the Second World War by John Gallehawk

Bletchley Park Report No. 13 Published May 2010

This booklet describes briefly the pre-war breaking of the German ENIGMA cipher system and the famous meeting in July 1939 when this work was revealed to the British and French Intelligence Services.






Convoys & U-Boats by John Gallehawk

Bletchley Park Report No. 7 Published September 2009







Enigma and the Bombe by Frank Carter & John Gallehawk

Bletchley Park Reports Published by September 2009








Figuring It Out at Bletchley Park 1939 – 1945 by John Gallehawk & Kerry Howard

Published by BookTower Publishing 2007 ISBN 978 0 9557164 2 3


During the last week of World War 2, Bletchley Park and its outstations had:

– 10,471 personnel, including 226 from the USA,

– 8,902 billets

– 33, 003 miles driven by 130 drivers transporting staff to and from Bletchley Park

– 22, 054 meals were consumed

Based on official wartime records held at the National Archives, Figuring It Out at Bletchley Park 1939 -1945 chronicles the extraordinary growth of the Government Code and Cypher School’s codebreaking operation at Bletchley Park during World War 2. This book of numerical tables is a transcription of the weekly returns Sir Edward Travis demanded to be kept from 1942.

This essential reference book places valuable weekly figures for World War 2 service and civilian personnel, their departments, accommodation, transport, catering requirements and achievements at the fingertips of any military historian, veteran or local history enthusiast.


Please note: I reserve the right to delete comments that are offensive or off-topic.

Leave a Reply

One thought on “John Gallehawk

  1. I have just read and analyzed the data given in your excellent Report No 7 “Convoys and U boats”, which I bought while on a fascinating recent visit to the Park.

    I am a US researcher in risk analysis, and so was interested in whether the anti-submarine data showed any evidence of learning how to sink them – and hence also understand any influence of naval code breaking.

    So I would like to ask you and/or your colleagues an important question. First I must describe my analysis.

    I transcribed the data from your Chart 5 into Excel files and calculated the survival probability, p (1- n/N, a measure of how likely the U boats were to survive) and the rate of sinking, R ( how effective the anti-sub measures were).

    To remove the arbitrary calendar year influence, a measure of the U-boat risk exposure ( or sinking opportunity) is needed. So the risk exposure measure was the number of U boats existing or operational ,N, times the number of their operational days at sea since 1939, quarter by quarter, D= Nxd ( a total of about 4 million sub-days) The number sunk , n, each and every quarter was also taken directly from the line shown in Chart 5.

    The rate definition takes into account the changing number of U boats that are operational at any time.

    The results are shown in the two graphs attached to this note.

    The probability of a U boat surviving, 1- n/N, declines as it should to about a 50:50 chance as more were sunk.

    However, the sinking rate shows that it remarkably became almost constant and remained at about 0.00001 during the entire interval ( after about the first year or so).This trend is not obvious from the raw data plot, as the number of sinkings is given only as an accumulated number in Chart 5.

    The sinking rate might be expected to rise as better measures and decoding became available.

    So why is it nearly constant? Were countermeasures not improving? Were codes not being broken? Were U boats harder to sink? And if course, the old key question of interest to you at Bletchley , does this constant rate reflects a deliberate effort to avoid disclosing the code breaking?

    I would s welcome any answers, reactions, thoughts, comments or ideas you and/or your colleagues may have.

    Thank you

    Romney B Duffey

    PS You can Google my name to find out more about me if you wish.