The first rule of The Mousetrap is you do not talk about The Mousetrap.

Okay, you can talk about it but you can’t give away the ending. Being induced to confidentiality by the cast at the curtain call makes you feel like you’ve been drawn into a secret club. This classic mystery has broken records as the longest running play in the world. Performed since 1952, the famous thriller is now on tour across the UK. The packed auditorium on its opening night at Theatre Royal Windsor was a testament to the play’s enduring popularity.

So why is The Mousetrap so successful? A large part of this is the best-selling author: Agatha Christie. You feel safe in the hands of one of the world’s most loved crime fiction writers. As she said herself, it’s not too horrible, frightening or farcical but it has enough of all of these factors to satisfy everyone.

The first act starts in darkness, we hear the dying screams of a woman being killed and the nursery rhyme ‘Three Blind Mice’ being whistled.

We’re then brought to a completely different scene - the opening day of Monkswell Manor guest house, run by Mollie and Giles Ralston. Harriet Hare and Nick Biadon give us this youthful husband and wife. The action takes place in a traditional wood panelled room that is elegant but comfortably furnished with chintz covered chairs, patterned rugs, painted portraits of aristocrats, a large leaded light window and a wood fire.

Radio reportage of the crime is playing as Mollie prepares for her first clients to turn up and we hear that the police are looking for a man in a dark overcoat, light scarf and felt hat. As each character arrives, there is comic suspense as they are all wearing outfits that fit this description. The first guest to enter Monkswell Manor is the young, excitable and nosily intrusive architect, Christopher Wren (played with ebullience by Lewis Chandler). He’s a bright contrast with the next arrival, the haughty Mrs Boyle who instantly finds fault with everything.

Unfortunately, Susan Penhaligon was ill on the opening night, however, Judith Rae stepped in and gave us a wonderful performance as this demanding, unlikeable character. John Griffiths ambles in as the jovial Major Metcalf and lets us know that the winter storm outside is getting heavier. Saskia Vaigncourt-Strallen arrives as the fourth expected resident; Miss Casewell. A handsome confident woman dressed in manly garb.

However, she is not the final customer, the mysterious Mr Paravicini (David Alcock) blusters in as his car has been trapped by snow and he pleads a room for the night. His exaggerated gestures and ham European accent are what we’d expect from Agatha Christie’s mid twentieth century tale. Before the hosts and their guests become too comfortable, there’s a phone call letting Mollie know that the Manor has been connected to the London murder and a policeman will be coming to protect them. Sergeant Trotter (played by Geoff Arnold) has to ski to the guest house as the roads have become impassable.

The weather traps the company together. As darkness falls, one of the members of the household is murdered. As the dastardly deed is done, the felon whistles Three Blind Mice. That nursery rhyme is actually really gruesome - what with tails being cut off with a carving knife!

The mood changes abruptly, everyone is a suspect and each lacks a convincing alibi. The group squirm as the plot thickens and we race to the finale...that I won’t give away.

Although The Mousetrap has darkness at its heart, it skates on the edge of the macabre without delving too deep. Agatha Christie’s plot skips and pivots to a clever twist at the end. You won’t be disappointed with this enthralling drama. You’ll have to watch it to find out whodunnit.