Alan Turing

Julius and Ethel married on 1 October 1907 at Bartholomew's church on Clyde Road, in Dublin.

Julius's work with the ICS brought the family to British India, where his grandfather had been a general in the Bengal Army.

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 computer science, providing a formalisation of the concepts of algorithm and computation with the Turing machine, which can be considered a model of a general-purpose computer.

He is widely considered to be the father of theoretical computer science and artificial intelligence.

Born in Maida Vale, London, Turing was raised in southern England.

He graduated from King's College, Cambridge, with a degree in mathematics.

Whilst he was a fellow at Cambridge, he published a proof demonstrating that some purely mathematical yes–no questions can never be answered by computation.

He defined a Turing machine and proved that the halting problem for Turing machines is undecidable.

However, both Julius and Ethel wanted their children to be brought up in Britain, so they moved to Maida Vale, London, where Alan Turing was born on 23 June 1912, as recorded by a blue plaque on the outside of the house of his birth, later the Colonnade Hotel.

In 1938, he earned his PhD from the Department of Mathematics at Princeton University.

During the Second World War, Turing worked for the Government Code and Cypher School at Bletchley Park, Britain's codebreaking centre that produced Ultra intelligence.

For a time he led Hut 8, the section that was responsible for German naval cryptanalysis.

Here, he devised a number of techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bomba method, an electromechanical machine that could find settings for the Enigma machine.

Turing played a crucial role in cracking intercepted coded messages that enabled the Allies to defeat the Axis powers in many crucial engagements, including the Battle of the Atlantic.

A number of sources state that Winston Churchill said that Turing made the single biggest contribution to Allied victory in the war against Nazi Germany.

However, both the Churchill Centre and Turing's biographer Andrew Hodges have stated they know of no documentary evidence to support this claim, nor of the date or context in which Churchill supposedly said it, and the Churchill Centre lists it among their Churchill 'Myths', see and A BBC News profile piece that repeated the Churchill claim has subsequently been amended to say there is no evidence for it.

See Official war historian Harry Hinsley estimated that this work shortened the war in Europe by more than two years but added the caveat that this did not account for the use of the atomic bomb and other eventualities.

In 1948, Turing joined Max Newman's Computing Machine Laboratory at the Victoria University of Manchester, where he helped develop the Manchester computers and became interested in mathematical biology.

Turing was prosecuted in 1952 for homosexual acts.

He accepted hormone treatment with DES, a procedure commonly referred to as chemical castration, as an alternative to prison.

Turing died on 7 June 1954, 16 days before his 42nd birthday, from cyanide poisoning.

An inquest determined his death as a suicide, but it has been noted that the known evidence is also consistent with accidental poisoning.

He wrote a paper on the chemical basis of morphogenesis and predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, first observed in the 1960s.

Despite these accomplishments, Turing was never fully recognised in Britain during his lifetime because much of his work was covered by the Official Secrets Act.

Transcript of a lecture given on Tuesday 19 October 1993 at Cambridge University

After the war, Turing worked at the National Physical Laboratory, where he designed the Automatic Computing Engine, one of the first designs for a stored-program computer.

Following a public campaign in 2009, British prime minister Gordon Brown made an official public apology on behalf of the government for "the appalling way [Turing] was treated".

Turing had an elder brother, John Ferrier Turing, father of Sir John Dermot Turing, 12th Baronet of the Turing baronets.

Turing's father's civil service commission was still active during Turing's childhood years, and his parents travelled between Hastings in the United Kingdom and India, leaving their two sons to stay with a retired Army couple.

At Hastings, Turing stayed at Baston Lodge, Upper Maze Hill, St Leonards-on-Sea, now marked with a blue plaque.

Queen Elizabeth II granted a posthumous pardon in 2013.

The term "Alan Turing law" is now used informally to refer to a 2017 law in the United Kingdom that retroactively pardoned men cautioned or convicted under historical legislation that outlawed homosexual acts.

Turing has an extensive legacy with statues of him and many things named after him, including an annual award for computer science innovations.

He appears on the current Bank of England £50 note, which was released on 23 June 2021 to coincide with his birthday.

A 2019 BBC series, as voted by the audience, named him the greatest person of the 20th century.

Turing was born in Maida Vale, London, while his father, Julius Mathison Turing was on leave from his position with the Indian Civil Service (ICS) of the British Raj government at Chatrapur, then in the Madras Presidency and presently in Odisha state, in India.

Turing's father was the son of a clergyman, the Rev. John Robert Turing, from a Scottish family of merchants that had been based in the Netherlands and included a baronet.

Turing's mother, Julius's wife, was Ethel Sara Turing (Stoney), daughter of Edward Waller Stoney, chief engineer of the Madras Railways.

The Stoneys were a Protestant Anglo-Irish gentry family from both County Tipperary and County Longford, while Ethel herself had spent much of her childhood in County Clare.