Heston has suffered violence at the hands of Marina on a number of occasions over the past few months, but has stuck by her in the desperate hope that she will change her ways.
However, Heston will soon reach breaking point as Marina lashes out once again - which leads to him losing his temper and ending their relationship for good.
Digital Spy recently caught up with Owen Brenman, who plays Heston, to hear his thoughts on the hard-hitting storyline.
What has the Heston and Marina story been like to film?
"Although it was an upsetting and traumatic storyline for Heston, it was great to do it from an acting point of view. It put my character into a position that he hadn't been in before, and it was exciting because we don't often see stories like this on television. Marian McLoughlin, who played Marina, was great to work with and that also made a huge difference."
What can we expect from the next few episodes?
"Marina's abuse gets a lot nastier, and Heston ends up quite broken because of it. That was challenging to do, but it's always nice to be taken out of your comfort zone."
Why has Heston stuck with Marina through all the violence?
"When the Doctors team were trying to work out the storyline, one of the senior producers told me this was their worry - why would Heston put up with it for so long? But I said that I could understand that, because he's been unlucky in his past relationships and therefore he's desperate for this one to succeed. That means that Heston has put up with a lot of rubbish that other people may not have done."
"By this point, Marina has been very cruel and very violent, but she's also a very disturbed character. Heston has been trying to help her for so long, but he finally just grabs her and throws her up against the wall.
"It's the first time that Marina has had that done to her, and she's quite shocked by it. Heston tells Marina how her mistreatment has affected him, and she's genuinely very scared herself. Heston raises his hand, hits the wall just a few inches away from her face, and throws Marina out."
What happens next?
"Heston becomes very depressed. He stays up all night, and then he goes into work the following day covered in blood and everyone is stunned. Heston goes into Julia's office and, very matter-of-factly, tells her what's happened. He's quite ashamed that he's been lying for so long, as he's made a formal complaint against Kevin after he became suspicious. You'll see him apologise, and it's a real low point for Heston."
Has the story been getting a good response from viewers?
"Yes, the reaction that I've been getting on Twitter and on the street has been very positive. A woman who lives nearby even came knocking on my door the other day, because she'd been on holiday and Doctors hadn't recorded properly. She was desperate to know what had happened to Heston and Marina! That's a good sign and hopefully shows that it's working.
"There must be lots of people out there who are in the same position as Heston, but I imagine they're quite reluctant to own up to it. That happens to Heston, too, as when his colleagues find out the truth, he's very reluctant to talk about it."
"I think it does, yes. When you've got a programme that's on five days a week, I suppose it's difficult to come up with new storylines, but this seems quite new as I can't really remember any other soaps doing a story like this. But I suppose if the other soaps like it, they might start doing it as well!"
Even with Marina gone, will Heston's experience affect him for a while?
"Yes, he starts reacting differently to certain situations - for example, he gets burgled at one point and behaves badly. I can't say too much, but you'll see him get into some legal trouble because of his actions in trying to defend himself, as he oversteps the mark. I think the audience will be on his side, but he makes bad decisions because of what he's been through with Marina."
Could Heston ever get together with Mrs Tembe?
"Well, I get on very well with Lorna Laidlaw, who plays Mrs Tembe. I think it would be quite interesting, and I think the writers get a lot of comedy from those two characters. Heston seems oblivious to it, but I think Mrs Tembe has a deep respect for Heston and his old-fashioned outlook on life. There is a bond between them, but whether they'd ever be a couple, I don't know."
You've done some more directing for Doctors recently, haven't you?
"Yes, I've directed three more episodes which will be airing at the end of March. It was fantastic and very hard work. It was particularly difficult for me, because during my first week of preparation for directing, I was also filming the end of the Marina storyline every single day. But it's great to use a different part of my brain and work with actors in a different way. I hope to do more of it in the future."
"Yes, I do miss the stage as it's great to perform in front of a live audience. But the best thing about working on Doctors is that the people are so nice, and you also get an opportunity to play a wide range of storylines - from comedy to quite tragic material. A lot of actors don't get that, as often in this business you can get typecast in a certain kind of role. So I love the variety at Doctors."
Do you have fond memories of your time working on One Foot in the Grave?
"Yes, I loved working in the BBC TV Centre, which I hear is going to be closed, so it's almost like it's from another era. It was very different to filming on Doctors as it was a lot more intense - you didn't do anything for a few months, but then you all turned up and had to be funny at the drop of a hat.
"They were a nice bunch and I'm still in touch with Doreen Mantle, who played Mrs Warboys. Every now and again I speak to Richard Wilson too, and I'm also in contact with the writer David Renwick."
Do you ever wear bow ties like Heston?
"I don't, but maybe I should! I remember once I was sitting outside having lunch in Birmingham, and later on I read a tweet that said, 'Spotted Owen Brenman in town - not wearing a bow tie!' Maybe I should take a leaf out of Heston's book and dress a bit smarter!"
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Doctors airs weekdays at 1.45pm on BBC One.