Outlander actor Steven Cree on the childhood stars stealing the show in Edinburgh International Film Festival premiere

There’s an old adage in the entertainment business attributed to the legendary American comic WC Fields – ‘never work with children or animals’.

The official release poster for Martyrs Lane

The implication being children and animals will either be maddeningly unpredictable or inevitably steal the scene.

It’s been 20 years since I left drama school, and I can safely say I love working with both children and animals, though I wouldn’t be in a rush to repeat the filming experience I had with 14 rats running all over me (rats are also known to urinate when nervous).

Steven Cree and Keira Thompson in the film Martyrs Lane

In the case of Martyrs Lane, screening at the Edinburgh International Film Festival (EIFF) this month and being released on AMC Networks-owned platform Shudder in September, I had the good fortune of working with two absolutely fantastic child performers Kiera Thompson and Sienna Sayer.

Martyrs Lane is about grief and loss, and how each member of a family handles those in their own way.

The themes are beautifully woven into a supernatural genre piece by writer/director Ruth Platt and explored through the eyes of ten-year-old Leah (Thompson).

Considering both Keira and Sienna were only ten years old at the time of filming, I was in awe at their natural ability, professionalism and the commitment they each brought to their roles.

Martyrs Lane premieres at the Edinburgh International Film Festival

Keira is in almost every scene of the film and leads the line with absolute aplomb.

Making a film for adult audiences told through the eyes of children is no mean feat, but I think Ruth manages to execute it wonderfully.

We are effortlessly transported into Leah’s world and the journey of discovery she goes on, and although we experience the uncovering of a family trauma through her eyes, it is intensely affecting.

Steven Cree. Picture: Photography by Pip

It must be said that Ruth and the casting director Jessie Frost did a fantastic job in finding Keira and Sienna.

The young actresses’ chemistry is essential for the success of the film, and they work sublimely together. On set, their enthusiasm was infectious – it was clear how much each enjoyed the other’s company.

That’s just one of the great things about having children around – they can lift any mood and bring a vitality and energy to proceedings.

Since becoming a parent, father-daughter relationships in scripts have appealed to me even more, and it was a huge part of the draw for me when I read Martyrs Lane for the first time.

Steven Cree as Gallowglass (nearest to camera) in A Discovery of Witches

I play Father Thomas, the vicar of the vicarage in which the film is set, and also Leah’s father. I shared several scenes with Keira and was continually impressed by her.

Children have a fantastic ability to be in the moment, something I think many of us lose in adulthood as our lives and brains get busier.

I marvel daily at how in the here and now my three-year-old is, and how that forces me to be present – or at least try to be.

With it comes an instinctual quality and a lack of self-consciousness which Keira has in spades. It made working with her a real joy and definitely shifted my performance and influenced my choices in the moment.

Martyrs Lane is a haunting and beautiful story that has stayed with me since shooting the film, and hopefully will stay with the viewers after seeing it.

Martyrs Lane, starring Steven Cree, Denise Gough, Hannah Rae and Anastasia Hille, plays at EIFF on August 20, 22 and 25, and will stream on Shudder from next month.

- Steven Cree is a Scottish film, television, and theatre actor and has starred in Outlander and Discovery of Witches.