author
Known for lively early-20th-century biographies, this writer focused on big public figures of the day, including novelist Marie Corelli, Prime Minister Lord Rosebery, and Salvation Army founder William Booth.

by Thomas F. G. Coates, R. S. Warren (Robert Stanley Warren) Bell
Thomas F. G. Coates was a biographer whose surviving record online is quite slim, but his books show a clear interest in prominent British literary, political, and religious figures. Works attributed to him include Lord Rosebery, His Life and Speeches, The Prophet of the Poor: The Life-Story of General Booth, and Marie Corelli: The Writer and the Woman.
Available catalog and archive records place those books around the turn of the 20th century, with Lord Rosebery, His Life and Speeches published in 1900 and Marie Corelli: The Writer and the Woman appearing in 1903. The Corelli book was written with R. S. Warren Bell, suggesting Coates also worked collaboratively when a subject called for it.
Beyond those publications, I couldn't confirm many personal details such as his birth, death, or wider career with confidence. Even so, the books that remain point to an author drawn to strong personalities and public influence, and to a style rooted in biography as a way of explaining the people shaping British cultural life.