Okewood of the Secret Service, by Valentine Williams (epub/Kindle/pdf)
George Valentine Williams (1883-1946) was an English journalist, actor, lecturer and screenwriter. He created "The Fox" (Baron Alexis de Bahl), "Clubfoot" (Dr Adolph Grunt), Mr Treadgold the tailor and Detective Sergeant Trevor Dene. He also wrote one book under the name Valentine Douglas.
This is the first volume in the Adolph Grunt series.