I’m grateful to my readers for some of these corrections. Simon Lavington (SL) generously read the text closely and provided me, after print publication, with a number of corrections to my facts, and some enlightening judgements. Professor Lavington’s book on the Mark I machines will be published in 2019.


Figure 7 appears in John Dummelow, 1899-1949, Manchester: Metropolitan-Vickers Electrical Company Limited, 1949 as mentioned in the Figure Notes but omitted from the reference list.

Figure 43 is from a Ferranti internal report of January 1954. There is a copy in University of Manchester Special Collections NAHC/FER/C/13b.

Notes and queries

On p53 I have confused the Telecommunications Research Establishment in Malvern and the Post Office Research Station in Dollis Hill.

p54 Figure 38. The dot in William’s Figure is in Sweden, not Norway. I don’t know what installation this refers to.

The arithmetic in Figure 43 on p61 appears wrong, but only because I cropped out a line item at the top where Ferranti had also predicted £100K of commercial sales. Looking at it now, I wonder if they hit their target.

p115 Ida Fitzgerald was the lone wirewoman in the University lab, and the woman photographed is not (necessarily) doing a wirewoman’s job, but she was doing it in Ferranti. So the identification of the woman in the photograph as Fitzgerald is less than likely.

p116: Alan Turing’s secretary was S J Wagstaff (SL).

p119: There is doubt as to whether Mary Croarken had worked in Hartree’s group (SL). I have somewhat mangled the physical tasks of using the Mark I and the reader is best referred back to the original sources.

p145: In the service of a throwaway gag about two and a half machines (the third Atlas machine was not sold at anything like list price) I’ve given the poorly sourced impression that the project was a failure on its own terms, but that whether or not that it is true should not obscure its considerable technical achievements.

In Note 9, the neuron estimates were actually a million, a thousand million, and ten thousand million.

Note 38 says that the history of Noel Teulon Porter and the Half Moon Club is still to be written. After publication I came across Philip Pattenden’s article in the 2005/6 Peterhouse Annual Record, which covers most but not all of the sources I know. Thanks to the Librarian at Peterhouse College Cambridge for supplying a copy.

Over-hypen-ation and tpyos

p10 second para line 2: missing ‘been’.

p43, 7 lines from bottom: extra ‘was’.

p110 Sun-day

p163 second line: ‘you can’t see them both’.