Question: Michael Arbuthnot Ashcroft,  was a code breaker at Bletchley Park during World War II, working in Hut 8 under which English computer scientist, mathematician, logician, cryptanalyst, philosopher and theoretical biologist?

Context paragraphs:
Banburismus: Banburismus was a cryptanalytic process developed by Alan Turing at Bletchley Park in England during the Second World War.  It was used by Bletchley Park's Hut 8 to help break German "Kriegsmarine" (naval) messages enciphered on Enigma machines.  The process used sequential conditional probability to infer information about the likely settings of the Enigma machine.  It gave rise to Turing's invention of the "ban" as a measure of the weight of evidence in favour of a hypothesis.  This concept was later applied in Turingery and all the other methods used for breaking the Lorenz cipher.

Alan Turing: Alan Mathison Turing ( ; 23 June 1912 – 7 June 1954) was an English computer scientist, mathematician, logician, cryptanalyst, philosopher and theoretical biologist.

Hut 4: Hut 4 was a wartime section of the Government Code and Cypher School (GC&CS) at Bletchley Park tasked with the translation, interpretation and distribution of "Kriegsmarine" (German navy) messages deciphered by Hut 8.  The messages were largely encrypted by Enigma machines.  As the Kriegsmarine operated Enigma more securely, Hut 8 had less information for Ultra than Hut 6 which handled Army and Air Force messages.  Hut 4 also broke various hand cyphers and some Italian naval traffic.

Michael Arbuthnot Ashcroft: Michael Arbuthnot Ashcroft (1920–1949) was a code breaker at Bletchley Park during World War II, working in Hut 8 under Alan Turing.

Hut 8: Hut 8 was a section in the Government Code and Cypher School (GC&CS) at Bletchley Park (the British World War II codebreaking station) tasked with solving German naval (Kriegsmarine) Enigma messages.  The section was led initially by Alan Turing.  He was succeeded in November 1942 by his deputy, Hugh Alexander.  Patrick Mahon succeeded Alexander in September 1944.

Betty Webb (code breaker): Betty Webb (born 1923) worked as a code breaker at Bletchley Park during World War II.  She contributed to the work of breaking the German cipher Enigma.

Susan Elizabeth Black: Susan Elizabeth Black {'1': ", '2': ", '3': ", '4': "} (born 1962) is a British computer scientist, academic and social entrepreneur.  She has been instrumental in saving Bletchley Park, the site of World War II codebreaking, with her "Saving Bletchley Park" campaign.

Dorothy Du Boisson: Dorothy Du Boisson, MBE (26 November 1919, – 1 February 2013) was a code breaker stationed at Bletchley Park during World War II.

Jean Valentine (bombe operator): Jean Valentine (born 1924, Scotland) was an operator of the bombe decryption device in Hut 11 at Bletchley Park in England, designed by Alan Turing and others during World War II.  She was a member of the "Wrens" (Women's Royal Naval Service, WRNS).  She was one of a number of women who worked at Bletchley Park.  During this time, she lived in Steeple Claydon in Buckinghamshire.  She started working on 15 shillings (75 pence) a week.  Along with her co-workers, she remained quiet about her war work until the mid-1970s.

Hut 6: Hut 6 was a wartime section of the Government Code and Cypher School (GC&CS) at Bletchley Park, Buckinghamshire, Britain, tasked with the solution of German Army and Air Force Enigma machine cyphers.  Hut 8, by contrast, attacked Naval Enigma.  Hut 6 was established at the initiative of Gordon Welchman, and was run initially by Welchman and fellow Cambridge mathematician John Jeffreys.

Supporting paragraphs: Michael Arbuthnot Ashcroft Alan Turing
Answer: Alan Turing