I can remember the exact moment I thought it would be cool to be an assassin. It was seeing Lucy Liu as the cut-throat O-ren Ishii strutting along a corridor with her pack of killers to the epic opening chords of "Battle Without Honour or Humanity" by Tomoyasu Hotei. The film was Kill Bill, and yes I loved Uma Thurman’s take-no-prisoners Bride but it was the Liu swagger walk that was a truly stand-out moment. Usually when women in movies do the slo-mo strut to music it’s to show off their beauty. A hair swish. A tight dress. Jaws are dropping at her looks. Yet here was a woman doing the slo-mo strut and the power in her walk wasn’t down to how she looked, but because of what she could do. A ruthless highly skilled killer. She wasn’t so much making jaws drop but heads roll. Literally.

The Nursery

The Nursery

When I look back on all my favourite characters growing up - Nancy Drew (Girl Detective books) Buffy Summers (Buffy the Vampire Slayer TV series), Sydney Bristow (Alias TV series) and Nikita (La Femma Nikita movie) - they all shared a skill, sass and fearlessness that were to be admired. They were the ones in charge - the men relegated to sidekicks, love interests, eye candy, unworthy enemies.

Later on Carrie Mathison (Homeland TV series), Jessica Reel (David Baldacci’s Will Robie books), Faith Mitchell (Karin Slaughter’s Will Trent books) and Kathryn Dance (Jeffery Deaver’s books) were whose brilliance shone to me in their work for covert government agencies.

Late one night when crawling out my kids’ bedroom, having finally settled our youngest, I found myself thinking of all these women and their super-skills. Surely if I had some kind of elite training I could manage escaping out of there without waking the baby? What would it be like to be a working mother… when work was violent and top secret? Imagining the juggling of two very different lives – the plastic matting of soft play and toddler cries, versus long-range rifles and reluctant interviewees’ screams - was how I came to create Lex Tyler. Lex is an assassin for a covert branch of Her Majesty’s Secret Services and a new mother. In my books Killing It and The Nursery Lex has to face down sleep deprivation, teething, tantrums and the terrible twos - all whilst working on whatever mission of international importance she’s been assigned.

What draws us to assassins and spies is the excitement of a secret life, their deadly skills – and above all their power. In creating Lex I wanted to channel some of that power into a character who could not only kick ass when it came to baddies, but when it came to being a working mother too. Lex could easily pull off a swagger walk like O-ren Ishi – except the strut in her step would be not just down to being an elite killer finishing a successful mission… but because she’s getting home in time for bath-time.