Over the course of three series we've seen therapist Paul Weston (Gabriel Byrne) treat many patients. But who made the most emotional impact on the audience? Here are my top three - and if you don't agree, feel free to nominate your favourites in the comments section below...  

Walter

“I finally have the time to talk to you but it’s too late for you to help”

You probably know John Mahoney best as irascible ex-cop Marty Crane in Frasier. But within a few minutes of him bustling into Paul Weston’s office, you forgot all about Marty. Here was Walter Barnett, embattled CEO, struggling to assert control over his life but plagued by insomnia and the panic attacks that have crippled him since childhood.

Walter rebuffs Paul’s attempts to change his behaviour until he hits an emotional wall – the shock of losing his job combining with his intense feelings of guilt over his brother’s death at 16 - and attempts suicide. Mahoney’s touching performance throughout guaranteed that when the floodgates opened for Walter, they opened for the audience, too.

April

“April, would you rather die than be weak?”

Another patient who wouldn’t let herself be helped, April’s (Alison Pill) case was particularly frustrating. The bright architecture student had been diagnosed with cancer but she wasn’t planning on having chemotherapy – and she certainly didn’t want anybody to know she was ill. She didn’t even want to know herself – the scene where she writes down her diagnosis for Paul to see, but first silently reads it back to herself, is heartbreaking.

Torn between reacting to her situation as a therapist or as a father, Paul found himself the target of many emotional confrontations on April’s road to recovery as he tried to get to the root of her fierce independence. But the two also shared a mordant sense of humour, leading to several scenes pleasantly reminiscent of exchanges with young first-series patient Sophie.

Sophie

“So…you want me to forgive myself. How?”

Gymnast and Olympic hopeful Sophie would have been easy to dislike: wilful, defiant, sarcastic and particularly vicious to her long-suffering mother. But young actress Mia Wasikowska made the most of Sophie’s waspish sense of humour and, when the chinks in her teenage armour were fleetingly revealed, made sure we saw the sad, damaged child forced too young to cope with the stresses of the adult world.

Abandoned by her father and caught up in an inappropriate relationship with her sports coach, it took Sophie a long time to realise she’d spent years blaming the wrong people for the unhappiness that led her to attempt suicide...

In Treatment concludes with a run of four episodes from 10:15pm Christmas Eve on Sky Atlantic