It was gripping but not easy viewing and I did feel a bit wrung out by the end! Even though credibility was stretched at times, the series did graphically illustrate what can so easily happen to the children when one of the parties to a break-up is a narcissist.

For those who didn’t watch, Tom was the long-suffering teenage son of Dr Gemma Foster and her husband Simon, who split up because Simon had an affair – and then a child – with a younger woman. The problem, over and above the normal challenges of a divorce, was that Simon was a narcissist. Gemma probably didn’t realise this; she must have known that he was selfish but there’s more to narcissism than selfishness.

A narcissist needs to have his own way and will exploit and manipulate others to get it, just as Simon manipulated Tom to get him to live with him, rather than his mother.

A narcissist is often preoccupied with fantasies of unlimited success. Unfortunately their fantasies don’t usually come crashing down around them in such spectacular fashion as Simon’s did when he lost his wife, his home and his business all in the space of a few hours.

A narcissist like Simon may run up huge debts because they feel entitled to the best of everything, because they can, and of course because they’re worth it.

A narcissist neither knows nor cares how others are feeling and shows no empathy, as poor Tom learned so cruelly from his father when he threw him out of his house, brushing him off with the words: “I’ll bring your things round later”.

Would Gemma have reacted differently if she’d been more aware of what she was dealing with?

There’s only one rule when leaving a narcissist: disengage totally. To be clear, this means walk out (or in some cases run) and don’t look back. Ever. A narcissist feeds on your attention and your empathy and you must cease to supply even the tiniest drop of either. If you have to communicate with them about your children you need to do it in writing and in the smallest possible number of words.

Dr Foster failed spectacularly to do this. She couldn’t keep away from Simon, the sparks flew, and young Tom was caught in the cross-fire. Gemma appeared unhinged at times, which was hardly surprising. Narcissists mess with your head and she’d lived with one for many years. Add to that the shock of discovering her husband’s affair and it’s understandable that she would fall apart.

Where did this leave Tom? In short, rudderless and acting out in a major way in school. Caught in the fight between a father who was never capable of caring about him, and a mother who could focus only on her ex, he could cope with the escalating dramas no longer, and walked out of their lives. A dreadful outcome for any parent (with the exception of a narcissistic one of course) and the salutary lesson for anyone leaving a narcissist is not to fight them, you’re sure to lose.

There is more information about divorcing a narcissist in my book, A Better Way of Dealing with Divorce: