Editing Great Train Robbery (1963) (section)

==London investigation==
Despite the big breakthrough of the discovery of Leatherslade Farm, the investigation was not going well. The London side of the investigation then continued under Detective Chief Superintendent [[Tommy Butler]], who replaced Millen as head of the [[Flying Squad]] shortly after Millen was promoted to Deputy Commander under George Hatherill. On Monday 12 August 1963, Butler was appointed to head the police investigation of the London connection and quickly formed a six-man Train Robbery Squad. With Leatherslade Farm finally found on 13 August 1963, the day after Tommy Butler was appointed to head the London investigation, the Train Robbery Squad descended on the farm.<ref name="Crime 1972">Specialist in Crime (1972), Ernest Millen</ref>{{page needed|date=August 2020}}

The breakthrough came when Detective Chief Superintendent Millen met a distinguished barrister in a smoking room of an exclusive West End club who told him that someone was willing to inform on the gang.<ref name="Crime 1972"/>{{page needed|date=August 2020}} The process of talking to the informer was handled by Hatherill and Millen and they never divulged the identity of the informer to the detectives in their command. The informant had been jailed in a provincial prison just before the train robbery and was hoping to get parole and other favours from talking. He clearly did not know all the names perfectly, and a second informant (a woman) was able to fill in the gaps. Millen said in his book ''Specialist in Crime'', "the break-through with the informer came at a moment when I and my colleagues at the Yard were in a state of frustration almost approaching despair".<ref>Specialist in Crime (1972), Ernest Millen, P.208</ref> This process saw them get eighteen names to be passed on to detectives to match up with the list being prepared from fingerprints collected at Leatherslade. Hatherill and Millen decided to publish photos of the wanted men, despite strong protests from Tommy Butler and Frank Williams. This resulted in most of the robbers going to ground.

===Tommy Butler, the thief-taker===
[[Tommy Butler]] was a shrewd choice to take over the Flying Squad and in particular the Train Robbery Squad. He became arguably the most renowned head of the Flying Squad in its history. He was known variously as "Mr Flying Squad", as "One-day Tommy" for the speed with which he apprehended criminals and as the "Grey Fox" for his shrewdness. He was Scotland Yard's most formidable thief-taker and, as an unmarried man who still lived with his mother, he had a fanatical dedication to the job. Butler worked long hours and expected all members of the squad to do the same.

The squad later had to work out rotations whereby one member would go home to rest as otherwise they were getting only three hours of sleep per night and had no time to eat healthily or see their families. When the squad tried to get him to ease the working conditions, Butler was enraged and threatened to send them back to their normal duties. Butler was said to be very secretive, with [[Jack Slipper]] claiming in his book ''Slipper of the Yard'' (1981) that "he wouldn't even tell his own left hand what the right one was doing". This meant that Train Robbery Squad members were often dispatched on errands with no knowledge of how their tasks fitted into the overall investigation.

===Train Robbery Squad===
The six-man Train Robbery Squad consisted of Detective Inspector Frank Williams, Detective Sergeant Steve Moore, Detective Sergeant [[Jack Slipper]], Detective Sergeant Jim Nevill, Detective Sergeant Lou Van Dyck and Detective Constable Tommy Thorburn. The senior officer, Frank Williams, was a quiet man. His speciality was dealing with informants and he had the best working knowledge of the south London criminal fraternity in the force. One of the squad, Jack Slipper, would later become head of the Flying Squad and would still be involved in the case many years later.

===Post Office Investigation===
The Post Office Investigation Branch (IB) had to establish the amount of money stolen, £2,595,997.10s.0d. They also sought to identify what money had been taken so that the relevant banks could be notified. Deficiencies in High-Value Package carriage security were reported and secure carriages were immediately brought back into service. The installation of radios was recommended as a priority. The investigation was detailed in a report by Assistant Controller Richard Yates that was issued in May 1964.<ref name=PMA />