HAROLD CHARLES KENWORTHY – WW2 CONTRIBUTION TO CODEBREAKING AT BLETCHLEY PARK

(1892 - 1960 )

 

 

I was contacted by a gentleman in April 2023, who informed me that Harold Charles Kenworthy had been born in Tottenham and had been a prominent person within the wartime codebreaking exploits at Bletchley Park. I must confess that at this time I had no knowledge whatsoever regarding H.C Kenworthy so I set about to try and discover a little more.

Here are a few bullet points that help build a better picture of Harold Charles Kenworthy.

  •  Harold Charles Kenworthy was born at 20 Burlington Road, Tottenham. His birth Registration can be found  Q3 1892 in the Edmonton District

  • My Swain family, that includes Christina Swain, were living in nearby Siddons Road (no 19) at the time of the 1891 Census.

  • Indirect family Connection:  I was shocked to discover that I have an indirect family connection with Harold Charles Kenworthy. My Dad’s Aunt, Christina Swain had married a Herbert Charles Lee at Tottenham Register Office in 1896., It was the sister of Herbert Charles Lee, Bertha Alice Lee, who married Harold Richard Kenworthy. Thus, Bertha Alice Kenworthy was the sister-in-law of my Great Aunt.

  • The 1901 Census shows Harold Charles Kenworthy (age 8 Years) and his family still resident at 20 Burlington Road. His mother Alice Bertha Kenworthy (nee Lee) was age 32 and born in Bethnal Green. They also had a daughter named Bertha age 2 and a son Richard aged 1. Their father Harold Richard Kenworthy had an occupation as a Wines & Spirits Cellarman.



 

·        The 1911 Census shows Harold Charles Kenworthy and family at 20 Burlington Road. Harold is 18 years of age and working as a Clerk for a Music printing company.



·        In 1932 Harold Charles Kenworthy married Ivy Ford at All Hallows Church in Tottenham. Charles was still resident at 20 Burlington Road and his wife, Ivy Lilian Ford, had lived in Birkbeck Road that was less than ½ mile away from Burlington Road. Harold’s occupation was given as a technical assistant.

 


·        By the time the 1939 Register was conducted just prior to WW2, Harold and his wife Ivy had moved to Banstead in Surrey. It was interesting to note that his occupation is given as Civil Servant – Wireless Engineer – The receiver for the Metropolitan Police.

 


 

·        Clearly his experience with Wireless operations made him most valuable to Bletchley Park. For a short while he worked for the GPO at Denmark Hill and was later made Commander and head of operations at the ‘Receiving Station’ at Knockholt.  Wireless intercepts at Knockholt were fed directly to the codebreakers at Bletchley Park.

·    I attach copies from the Bletchley Park ‘Roll-of-Honour’ that help emphasise the important role that he played.





·        I have a book on my bookshelf titled ‘Colossus’ by Paul Gannon. Chapter Eight is devoted to the work done at Knockholt and has several references to Harold Kenworthy.

 

·        There is also an extract from a paper on ‘Breaking Ciphers at Bletchley Park’ that refers to Harold Kenworthy.

·        Harold Kenworthy died at Banstead, Surrey in 1960.

  

·        Probate Record – Charles Kenworthy’s’ estate was valued at £6,900 not an inconsiderable sum back in those days.

WW1 MILITARY SERVICE

It transpires that Harold Charles Kenworthy served during WW1 in the Royal Naval Volunteer Reserve, where he attained the rank of Temporary Sub-Lieutenant and was awarded a British War Medal. He also served in Gibraltar as the Port Wireless Operator. Another record makes reference to the Marconi Company so I’m guessing he would have been involved in wireless communications for the Royal Navy during this time. Harold’s younger brother Frederick Robert Kenworthy also worked in wireless communication.

METROPOLITAN POLICE – PIONEER POLICE CAR RADIOS.

In the inter war years Harold Kenworthy was a pioneer with the introduction of radio for police cars. He initially worked for Marconi and then joined the civilian staff of Metropolitan Police where he was Head of their intercept station at Scotland Yard, which was later moved to Denmark Hill.

 

 

KNOCKHOLT RADIO TRANSMITTER AND RECEIVING STATION

 

Intercepting teleprinter non-Morse transmissions was going to be an entirely different technical challenge from the interception of Enigma messages in Morse code, and a much tougher one, requiring new equipment, special techniques, and highly skilled staff.  It was decided by April 1942 that Harold Kenworthy should be moved from the intercept station at Denmark Hill to take charge at a new site of at least fifteen acres, allowing room for directional antennas and other equipment.

A location was needed that was some 200 metres above sea level, offered easy access for operators and was close to long distance telephone cables. After a site in Surrey was rejected, Ivy Farm ay Knockholt on the North Downs, not far from the affluent town of Sevenoaks in rural Kent, was chosen for the new non-Morse interception centre. 

It was as Harold Kenworthy later recalled. ‘A converted farmhouse’ which was requisitioned with upwards of 30 acres of land - subsequently extended to about 160 acres in July 1942. It was situated on a broad summit plateau at 240 metres.

 


 

The General Report on the breaking of the Tunny code at Bletchley Park contains many references to the interception station at Knockholt and a few to its subsidiary outstations, but gives little detail of how the work at these stations was carried out. Some of this missing detail is found in a series of reports, ultimately deriving from Harold Charles Kenworthy (1892–1960), the head of Government Communications Wireless Station (GCWS) Knockholt and of its attached laboratory and workshop, the Foreign Office Research and Development Establishment (FORDE).

 

BREAKING CIPHERS

The Emperor's Codes: The role of Bletchley Park in breaking Japan's secret ciphers.
This book pays a belated tribute to men like Harold Kenworthy, who with the help of the Metropolitan Police wireless staff, built the `J' machine, which in 1935 made the first mechanically-aided breach in Japanese codes, a year before the American Red Machine, and Captain John Tiltman, the Highland-reel dancing eccentric and Bletchley Park wizard, who on the eve of the Second World War first broke through tangles of the 30,000-word Japanese Operational Code and discovered how to strip away the cipher additives to reveal the encoded message within.

 

COLOSSUS – CODEBREAKING COMPUTER – BLETCHLEY PARK
Bletchley Park was the home of Colossus where the invention of the world’s first true computer had taken place. Few people were aware of the crucial part it played in winning the Second World War. It demonstrated how, through a combination of intellect and intuition, improvisation and application, the codebreakers at Bletchley Park broke into Nazi Germany’s most formidable cipher machine and eavesdropped on the Reich’s high command, and even Hitler himself.

The wireless intercepting station at Knockholt in Kent played a vital role in feeding this information to Bletchley Park. They would be handling Teleprinter non-Morse transmissions.  At first it was estimated that about eight interception sets would be needed (plus items such as filters that prevented interference), although this soon jumped to twenty-five sets, with the likelihood that of another seventy-five being needed shortly after that.

However, it was found the existing recording gear would not provide the necessary well-shaped signals and much work was put into the design of more suitable gear. The result was the development of a satisfactory bridge that would work with the Marconi Undulator equipment. This bridge was later called the Kenworthy Bridge. The prototypes were made at the Metropolitan Police Workshops at West Wickham.

As the quality of wireless interception improved, the codebreakers at Bletchley Park started to have more success. Intercepts from some new German radio stations were being broken with weeks of their going online. The very fact that this was done is the best measure of the efficacy of Kenworthy’s interception service.

 

Article written and prepared by Alan Swain - August 2023

My thanks to Roy Spratt for first alerting me to this Tottenham connection.