According to data reported by him in Spica (January 1973), Firebrace was born on 16 August 1889 at 5:00 p.m. AST, in Halifax, Nova Scotia, where his English father had an army post.

He acted as an observer and interpreter for Winston Churchill at the Potsdam and Yalta conferences[5] and when Molotov visited London in 1942[6][7] and ran the War Office Russian Liaison Group.

[10] During his service in military intelligence, Firebrace was involved (in 1944) in the affair surrounding the arrest and prosecution of Helen Duncan, a famous British spiritualist medium, under the Witchcraft Act 1735 (9 Geo.

[13] A big-framed man, known affectionately as "the Brig", Firebrace worked closely with the eminent siderealist Cyril Fagan (1896–1970) and gained a lifelong interest in sidereal astrology.

In 1916, Firebrace married Esme, eldest daughter of Henry Claud Lyall, of The Hurst, Headley, Surrey, of a landed gentry family.