Which Agatha Christie novel introduced Colonel Race?

Colonel Race was introduced in Agatha Christie’s novel The Man in the Brown Suit.

The novel was first published in the United Kingdom by The Bodley Head on 22 August 1924. Its heroine, Anne Beddingfeld, witnesses a suspicious death at a London Underground station and follows a cryptic clue connected with the ship Kilmorden Castle and a journey to southern Africa.

Colonel Race appears among the passengers and investigators drawn into the international conspiracy. He is portrayed as a wealthy, capable man with experience as a government agent, detective and lion hunter in Africa. His combination of authority, secrecy and adventure made him a natural recurring character.

Race later returned in three major Christie novels: Cards on the Table, Death on the Nile and Sparkling Cyanide. The latter title can mislead quiz-takers because Race appears there too, but it is not his debut. The Seven Dials Mystery and The Secret Adversary feature different casts and do not introduce Colonel Race.