Albert Leslie Yoxall (18 May 1914 – 30 September 2005)
was a British codebreaker at
Bletchley Park
Bletchley Park is an English country house and estate in Bletchley, Milton Keynes ( Buckinghamshire) that became the principal centre of Allied code-breaking during the Second World War. The mansion was constructed during the years following ...
during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
. He devised a method to assist in solving
Enigma messages which was dubbed Yoxallismus. After the war he worked at
GCHQ until the mid-1970s.
Early life
Yoxall was born in
Salford, and was the youngest out of four brothers.
His father died young in a
tramway accident.
Leslie Yoxall was educated at
Manchester Grammar School from 1925
["In Memoriam: Leslie Yoxall", Bletchley Park Newsletter, Spring 2006] and
Sidney Sussex College
Sidney Sussex College (referred to informally as "Sidney") is a constituent college of the University of Cambridge in England. The College was founded in 1596 under the terms of the will of Frances Sidney, Countess of Sussex (1531–1589), wife ...
,
Cambridge
Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge bec ...
from 1933, graduating with first-class honours. He received his doctorate in 1941.
On the outbreak of war, Yoxall returned to teach at
Manchester Grammar School,
and was next in line to become the head of mathematics.
[Hugh Sebag-Montefiore, ''Enigma: The Battle for the Code'', 2000, , p. 296]
Codebreaking at Bletchley Park
In April 1941,
Gordon Welchman wrote to Yoxall advising him that he would soon be asked to help with "war work".
In due course, Yoxall was invited to join Bletchley Park and was, alongside
Bill Tutte
William Thomas Tutte OC FRS FRSC (; 14 May 1917 – 2 May 2002) was an English and Canadian codebreaker and mathematician. During the Second World War, he made a brilliant and fundamental advance in cryptanalysis of the Lorenz cipher, a majo ...
, interviewed by
Hugh Alexander and then
Alan Turing
Alan Mathison Turing (; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing was highly influential in the development of theoretical com ...
.
Yoxall was selected to join the team in
Hut 8, working on Naval Enigma
as a "temporary junior administrative officer".
He worked on the problem of ''Offizier'' (Officer) messages, which had been enciphered on Enigma with a second setting for additional security. Yoxall discovered what became known as "Yoxallismus", a method for recovering the Offizier setting.
In October/November 1942,
[Ralph Erskine, "Breaking German Naval Enigma" in ''Action this Day'', edited by Ralph Erskine and Michael Smith, 2001, , p. 186] he moved to Hut 7
to work on a Japanese naval cipher, making a significant contribution in identifying how the cipher permutations were constructed.
Post-war work
After the war he moved to
Eastcote and then moved again with
GCHQ to
Cheltenham
Cheltenham (), also known as Cheltenham Spa, is a spa town and borough on the edge of the Cotswolds in the county of Gloucestershire, England. Cheltenham became known as a health and holiday spa town resort, following the discovery of mineral s ...
in 1953.
He worked in Washington as a liaison officer from 1959 to 1963, and returned again in 1968 to 1972.
After the first tour in the US, a letter sent to the director of GCHQ (
Clive Loehnis
Sir Clive Loehnis KCMG (24 August 1902 – 23 May 1992) was a director of the British signals intelligence agency, GCHQ, a post he held from 1960 to 1964.
Career
Loehnis was born in 1902 in Chelsea, London. His father, Herman Loehnis, was born in ...
) stated that "his superior technical competence and analytic insight have served as a stimulus to everyone with whom he came into contact. His engaging personality, diplomacy and tact have endeared him to us all".
He retired from GCHQ around 1974 and returned to teaching, tutoring and coaching students in mathematics.
References
{{DEFAULTSORT:Yoxall, Leslie
GCHQ cryptographers
People from Salford
Bletchley Park people
People educated at Manchester Grammar School
Alumni of Sidney Sussex College, Cambridge
1914 births
2005 deaths