Over 22 years, 116 episodes, and countless ever-more-innovative deaths, Midsomer Murders has left fans around the world with the simple satisfaction of a puzzle well solved as the credits roll.

If viewers want to get the most out of its 20th anniversary series, however, they will have had to be paying close attention.

The writers of Midsomer Murders have promised a smattering of hidden treats for loyal fans, as they place clever references to past episodes in its newest shows.

The insertion of in-jokes and hidden messages, which have become known as “Easter eggs”, are increasingly popular on television in the internet era, with fans swapping the things they have spotted on social media and forums.

The Royal Television Society recently noted that while planting messages for die-hard fans has been going on for decades, citing the cameos made by Alfred Hitchcock in his own films, the trend for “Easter eggs” has seemed “like a relatively new phenomenon” thanks to cult classics Doctor Who, Games of Thrones and Black Mirror.

Now, that venerable television institution Midsomer Murder has joined the fun.