Doc Martin (ITV, 9pm)

CAROLINE Catz is frequently asked why her character tolerates Doc Martin’s grumpy manner. “People say to me ‘why does she put up with him’. She puts up with him because she loves him, and he’s a really kind and considerate person who finds it really difficult to express himself, “ she says.

“You know he is good because you can see the way he is, and he has this great integrity. He is a real anti-hero in a way, in a great way. He has his own quirky charisma which she loves. I think it is interesting watching these two people try and be together. They are obviously attracted to one another. It is not sensible for them to have a relationship, but they love one another and that is a really common story. You see it all over the place. How many people are perfectly matched in every way?”

The Doc has been seeking the help of a psychotherapist to try to solve his problems and make their marriage work. But tonight Louisa is asked to join other couples in therapy sessions.

"This is quite funny because Dr Timoney (Emily Bevan) is a very good therapist and gets underneath what is really going on between the two of them, and I think that will be really satisfying for the audience.”

The production had worked with a real couples therapist, who had studied the characters and the dynamic between them, before writing the scripts.

“What we learn from this series is that they are probably going to drive each other mad for ever more. They do love each other very much. They go on a big journey in their relationship and with what is going to happen to them. Then true to the series there are so many mad, interesting and insane situations that take them on this other journey as well. All the things that Dr Timoney unearths all connect up. It’s not like we find out new information. It is all information we have heard before in previous episodes: a little bit about her dad, a bit about her mum.

“Those seeds have been planted way back earlier; that her dad was in prison, that her mum left her when she was really young. She was brought up by her dad, left to her own devices when she was about 17. All those things have been planted and it has just been really nice to see without realising all this stuff has been fed into the character and now we are getting the pay off.

“One of the things Dr Timoney suggests is that perhaps Louisa sets Martin challenges that he can’t possibly achieve in order for that cycle of people always leaving her to keep happening."

There's good news of sorts for John Marquez's PC Joe Penhale who is offered promotion to Exeter because his boss thinks that Portwenn's low crime-rate is all down to perfect policing.

After the previous series of Doc Martin, Caroline Catz went straight onto film another series of the ITV drama DCI Banks. This autumn she's filming a comedy drama with Ben Miller for the BBC, I Want My Wife Back.

Police Interceptors (Channel 5, 8pm)

PC Damo Stevens takes on an aggressive arsonist intent on bringing Darlington to a standstill, while dog handler Andy Hunt is called to a violent domestic disturbance. Sgt Kev Salter is hot on the heels of a runaway quad bike and PC Paul Jackson uses advanced stop tactics to apprehend a gang of suspected thieves.

Panorama (BBC1, 8pm)

THE programme goes inside one of the UK's largest frontline mental health trusts, following the teams through their daily decision-making process of who to let in and who to send home. The film shows nurses dealing with people who are suicidal, aggressive or isolated in their community, and hears how the system is so overloaded and other support services so depleted that staff feel they often struggle to meet all their patients' needs.