It was developed in the 1850s and 1860s, largely by Richard Albion Holliday of Newland Street.[1]
On 29 September 1933, Ernest Holloway Oldham was found dead at his home, 31 Pembroke Gardens with his head in a gas oven.[2] Oldham was a cipher clerk in the Foreign Office, but from 1929 until his death in 1933 was a Soviet spy for money, rather than some ideological motivation. Although ostensibly a suicide, it is just as likely that he was killed by the Soviets.[2] His wife Lucy King was found dead in The Thames in 1950.[3] It is possible that they were both killed by the Soviets or MI5.[3]