In the works of Agatha Christie, Colonel Ephraim Pikeaway is a recurrent character in several novels. He is a senior official heading an intelligence agency. In Cat Among the Pigeons, this is said to be "Special Branch". This is not necessarily exact but his duties there do seem consistent with what a Special Branch would do. In other stories his department is not mentioned specifically.
In Cat Among the Pigeons, Pikeaway is described as "always sleepy" and someone whose eyes always seemed to be closed. But this is deceptive. As Adam Goodman, one of his subordinates tells Poirot, "I’ve never seen him wide awake. When I do, I’ll know that for once he isn’t paying attention to what goes on."
Pikeaway is a crossover character who unites the Poirot and Tommy and Tuppence universes.