Brian Horace ClemensOBE (30 July 1931 – 10 January 2015) was an Englishscreenwriter and television producer, possibly best known for his work on The Avengers and The Professionals. Clemens was related to Mark Twain (Samuel Langhorne Clemens), a fact reflected in the naming of his two sons, Samuel Joshua Twain Clemens and George Langhorne Clemens.