What was the name of the Metropolitan Police detective who investigated the Great Train Robbery of 1963?

Jack Kenneth Slipper (20 April 1924 in London – 24 August 2005 in Pershore) was a Detective Chief Superintendent in the Metropolitan Police in London. He was known as "Slipper of the Yard" (referring to Scotland Yard).

Slipper is mainly notable for his role in investigating the Great Train Robbery in August 1963. Then a Detective Sergeant with the Flying Squad, Slipper was one of six police officers chosen by its head, Tommy Butler, to form a special unit to catch the robbers. According to the police investigation, several of the robbers had left fingerprints or palm prints at the gang's temporary hideout at Leatherslade Farm in Buckinghamshire. Biggs' fingerprints were found on a bottle of tomato sauce. Slipper was present when Biggs was arrested at his home in Redhill on 4 September 1963.

After being sentenced to 30 years imprisonment in 1964, Biggs escaped from Wandsworth Prison in 1965. Biggs travelled via Paris to Spain and then Melbourne, Australia, where, despite plastic surgery to alter his appearance, he was identified by his dental records after visiting a dentist.

In January 1968 after six years with the Flying Squad, and most of the wanted Train Robbers caught, Slipper decided to return to Division and gained promotion to Detective Chief Inspector in September of that year. After a few other postings, in March 1973 he returned to the Flying Squad as operational Chief Superintendent.