Inspector Japp

When Emily Inglethorp is poisoned at Styles in 1917, Scotland Yard sends Japp. He's quick to arrest and slow to doubt, and Poirot has to hold him back so the wrong suspect isn't taken at the wrong moment.

It starts a partnership full of jabs, where Japp gets the public credit and Poirot gets the answer. Japp never admits out loud that he needs the Belgian, but he never stops calling him when a case gets strange, and over time the rivalry turns into real friendship.

In Murder in the Mews, Japp and Poirot walk home from dinner on Guy Fawkes night, with fireworks going off all over town. The next morning Japp is called to the death of a young widow that looks like suicide, and he brings Poirot along.

Throughout the first series, Japp is the link to the police: he opens doors, brings reports and complains when Poirot solves it all first.

When a killer starts sending Poirot letters announcing murders in alphabetical order, Japp runs Scotland Yard's manhunt. He puts teams in the towns on the map, watches railway stations and backs the suspect all the evidence points to.

Poirot disagrees, and the two argue like old colleagues. Japp listens anyway, because he's learned the Belgian's odd ideas tend to be right, and in the end the Yard makes the arrest with the answer Poirot handed over.

When Poirot tries retiring to the country to grow marrows, Japp turns up in the village of King's Abbot for the Roger Ackroyd case. The two team up again, and once more Japp watches Poirot name a culprit he'd never have guessed.

In The Big Four, on the eve of war, Japp teams up with Poirot, Hastings and Miss Lemon again against a supposed secret organization behind a string of crimes. The case brings the old gang together one last time and tests the long friendship between the inspector and the detective.

On ITV, Philip Jackson played Japp from 1989 to 2002 and returned for The Big Four in 2013. He doesn't appear in the Ustinov or Branagh theatrical films; in the 2018 miniseries The ABC Murders, Japp is played by Kevin McNally.