Stephen Maddock (1897-1952) seems to have been a pseudonym for James Morgan Walsh, an Australian-born writer who moved to England. He focussed on spy stories, and his series character was the secret agent T. Terrel.

Bibliography

A Woman of Destiny (1933)

The White Siren (1934)

Gentlemen of the Night (1934)

Danger After Dark (1934)

Conspirators in Capri (1935)

The Eye at the Keyhole (1935)

Conspirators Three (1936)

Forbidden Frontiers (1936)

Conspirators at Large (1937)

Lamp-Post 592 (1938)

Doorway to Danger (1938)

Spies Along the Severn (1939)

Spades at Midnight (1940)

Date with a Spy (1941)

Step Aside to Death (1942)

Drums Beat at Dusk (1943)

Something on the Stairs (1944)

I'll Never Like Friday Again (1945)

Overture to Trouble (1946)

Exit Only (1947)

East of Piccadilly (1948)

Keep Your Fingers Crossed (1949)

Private Line (1950)

Public Mischief (1951)