Why did you take the decision that Series 10 would be the finale?

It just felt right for everyone involved. We would love to come to Cornwall and work here but we can't do every job down here.

It certainly felt, with this many episodes in, coming up with the stories, not just the individual stories but the through lines with the characters across the series and their journeys throughout it, it has just been done now, and I think we would be repeating ourselves. It just closes the circle.

I will never get a job as good as this again I know that in terms of what it has done for us personally, but also just in the sheer joy of it, not being in a city to film it, and being allowed to make something funny in front of a camera, which is my favourite work experience. To get to do it with this level of input, to have a voice in decisions, and to have it so loved. Nothing of what I am saying could have been predicted when we started. It was just another case of saying 'let's see if we can get this one away'.

The first series launched in 2004, did you ever imagine it would become as popular as it has become?

No because all you think of is how popular it needs to be to get a recommission. It is sort of quite mechanical in a way. Caroline Catz's husband Michael reminds me of what I said at the wrap party outside the village hall after the first series: "I wouldn't mind doing this for another ten years." I sort of light-heartedly said that. And here we are 18 years later.

What has been the reaction of the public who gather to watch the filming in the village to the news that this is the last series?

There were some people who said 'please don't stop'. But I think it has been a long time and it has been a great number of episodes so I think they appreciate that if we say it is time to stop, it is time to stop.

As an actor presumably you would like to move on to other roles?

Any employment takes you off the employment market doesn't it? I have been lucky enough to have done other things whilst doing this as well. Because it is every other year we film, it does take such a chunk out of - five months out of 24 is a lot less than five out of 12. I don't think I will work as much again, I will be surprised if I do. [He jokes]

You came to the role of Doc Martin after playing the affable character of William, the undertaker in the ITV drama William And Mary. The Doc couldn't be more different.

It was a leap. I need something to act, someone to act, or something to pin someone on rather than just open a script and a nice guy says some kind of nice things. William was an affable undertaker. But we made this up. It just seemed a good use of me, and also I am physically quite chaotic, and it is an attempt to impose some order on me, with this sharp short haircut, and the tailored suit, I am much stiller.

I noticed on the Platinum Jubilee Pageant I was moving about all over the place. So I am aware of stilling myself for this, and being economical because it suits the character. It remains a stretch for me and a challenge but also a good source of being funny.

One of the things you said in an interview for the very first series was "I really like having the opportunity to be loathsome" with the character.

He is sort of loathsome, but it has defined itself as the series has gone on. Sometimes a writer will write the Doc being unkind, but he isn't, he is just clear, he is just not kind, he is not unkind, he doesn't reach to be unpleasant to people. There is a dryness to him. It's fun to play.

What are your memories of making the first series?

I remember filming at the Camelford Hotel and walking into the door in the first series. It wasn't in the script, it was just an idea I had on the day, but it became quite a tone for me, a sort of benchmark for me because I had just been like super doc and diagnosed Louisa's eye condition on the spot, and I just thought 'whack him in the face for being so cocky'.

We have now done that with the Doc a few times with door frames and things.

What has happened to your character over the last ten series. Is he still as grumpy as ever?

He is as impatient with people as ever, but he is a happy parent. There's this dog which he tolerates for his son James's sake for instance. He has had to be reminded that as a parent you can't be single minded and bend everyone to your will, which is kind of reflected in the Christmas episode as well - that kind of thing of him evolving and learning that he needs to listen, and think of others a bit. His continuing love affair with his wife coupled with his lack of tolerance. Having her in practice in the same building has its penalties.

He realised he had to change to keep his marriage?

Yes but also we realised that whilst it was great fun to have this combative character, we believed that he needed a human heart so that has to move. That is where we have made the changes in him.

In this series there is another baby for the couple - Mary Elizabeth - who is named after our first cocker spaniel, Mary.

What have been the highlights of the last ten series?

It's a bit naff to say, but it has all been a highlight. There have been bits that stick in my memory - like abseiling down a cliff wearing a suit, normal shoes and and carrying a medical bag. That was out on the cliffs with dear old Richard Johnson. I had to do an emergency trepanning [perforating a person's skull] with a drill into the guy's head. I did actually do the abseiling, I did that walking out over the edge of the cliff which was quite alarming. I had the drill in one hand and the medical bag in the other.

You'd think a stunt man might have done that scene?

No it makes it better if you do it yourself.

Helicopters were always a highlight. Before we used drones we used helicopters for some shots, and we were always terribly excited when the helicopter came over. There was one scene where the helicopter flew into the harbour to film a scene with Caroline and I outside the Doc's house.

The helicopter was level with us, in the harbour, but then it flew off. All the crew were lying down under windows, hiding from the helicopter so they weren't caught in the shot. It's the sort of thing now you can do in five minutes with a drone.

Being allowed to pretend to fall in love with Caroline Catz every other year has been a big joy. It really is.

The series has attracted a huge array of guest stars over the years Sigourney Weaver, Danny Huston, Caroline Quentin - we were gutted that we couldn't find anything for a homeopathic vet - the character she has played - in this last series. We did really try to find something. Her daughter Rose is in an episode of this series, though.

Roger Lloyd Pack, Claire Bloom played my mother, Ben Miller was a crazy park ranger, Kenneth Cranham was Louisa's father, Richard Johnson was a curmudgeonly colonel, Julie Graham was PC Penhale's estranged wife, Anne Reid was a woman who ran a cat sanctuary.

Celia Imrie - her son Angus is in this series and he remembers coming with her as a boy to Port Isaac when she filmed an episode in the first series.

Have actors approached you to play a role?

Tom Conti is a good example. I'd never met Tom Conti, but I remember my mum taking me to see him in Whose Life Is It Anyway? at The Savoy all those years ago. He came up to us at a Dame Edna Everage event and said "I really like your show, it's the only witty thing on television" and it lodged in there, and we offered him the role of a surgeon who was scrutinising the Doc in the ninth series.

We have a standing joke on the series of making up funny names for the patients. I came up with one this morning: Robin Banks! With Jess, who plays the doc's receptionist Morwenna, we have a list of names on our phones that we have used. We kept the list in the appointments book on the desk of the surgery. Everybody contributes suggestions for funny names. The names are never in the script. Jess and I throw them in. I do it to surprise Philippa (Braithwaite, the producer) in the rushes.

What have you enjoyed most about making the series?

My favourite work experience is when everything is off the lorry in the middle of a field. That is when I am happiest because I just love the way a film crew works. I know what everybody does and appreciate the way that they do it. To be a part of that, amongst like minded friends is just jam. That's my job and that it is successful. I was happy in the field, but to have other people liking what we made as well in the way they have around the world it's mental. And of course the fact that I get to go to work with my wife [Philippa Braithwaite, the producer), and to be down here in Cornwall.

I can't pull out one thing and say that was the most enjoyable thing about making the series. But when I drive down here and as I approach Port Isaac and see the sun setting over the sea, the view is breath-taking.

We have rented the same house each time we came to film, apart from for the first series when we had a swishy house in Rock. Our daughter Emily was a baby then, and we had Mary the cocker spaniel.

The changes in your own family life have been reflected around the cast and crew?

Emily was a baby when we first went to Port Isaac, and she is 23 now. She was born during the filming of Saving Grace, and she was a toddler when we made the Sky films that preceded the ITV series. She came down with us, and went to the local nursery in Wadebridge, now she drives herself down to Port Isaac. So it became her second home too. She has been to every single visitor attraction in the area more than once.

She had a walk on part and dubbed an 'ouch' on the sound, but acting is not her thing. When she was very tiny she found it very weird seeing me working on set with people all round me, make up artists patting your face, having your tie adjusted by a costume assistant. She would watch on the monitor, and when they said cut she would rush in and sort of grab me. It was like putting herself between it and me. She would say 'was that you who said that' about what she'd seen me do and say on the monitor.

Chris Bird, the gaffer on this - I worked with his dad, the only gaffer to get an OBE, on Men Behaving Badly, and Chris used to go onto set with his dad, and now Chris's boy Harry comes out with Chris. We have all bounced into each other's kids every other year.

Caroline's daughter was born between series, Jess has had two boys since she started on the series, Joe moved to Cornwall and has three children.

What changes to the village have you seen since you first began filming in Port Isaac? What has it been like filming in the village now with so many fans eager to watch the action?

There's more people, especially out of season. We generally try not to be here during the season because enough people were coming in. That has increased.

I very seldom go into Port Isaac without a crew so I am buffered. But there are people I know and faces I recognise in the crowds.

Even though there's more people, we can still film in the village we just need a little more man power than we used to have to hold the crowds back. They are generally sweet. In London people will try to mess you up during filming by beeping their car horns for example. You don't get that here. In fact when we are filming we marshal the traffic through the village.

Do people still bring their dogs for you to make a fuss of?

People know that I love dogs. It makes it much easier for everyone because there is no awkwardness about what to say. I never tire of meeting the dogs, and seeing how people are with their dogs, it just opens conversations rather than this uncomfortable thing of them asking for a picture with me. But if they can get a picture of me with their dog, they are over the moon.

We used to bring our own dogs to Cornwall, but Heidi is blind, and where we stay there are lots of levels so she would be falling down all day long, and they are fine at home.

What will you miss most about not returning to Port Isaac?

Just being here. It is a lovely place. Famously acting is a lot about standing around and waiting, and the amount of time I have spent outside that surgery, just standing waiting and gazing out to that view over the harbour and out to sea, I don't think there is any point in my own garden where I have stood that long. Driving myself to work every morning through the lanes, seeing the sea. Just the whole vibe.

Would you come back here if you weren't working?

Probably not. It would be a bit odd to be walking around Port Isaac when I am not working. When Emily was little and she was here with us, my mum would come down, and people would visit us here, and we would go out on down days. But now, maybe because I am getting older, the minute I get some time off I go home because it is only two hours drive away. I don't really have down time. I always need something to do.

In Series 5 you bought a horse while you were here?

Yes, Ben Catel who I saw at the Royal Windsor Horse Show where I was for the Platinum Jubilee Pageant. We gave the horse to the costume designer on the early series. Ben is a Lusitano, a Portuguese dressage horse. We also bought Emily's pony Saracen from nearby Camelford where Emily went to the riding school there.

Do you have a souvenir from Port Isaac to remind you of your time there?

When we were building our farm I bought some Delabole slate to use. It looks really nice and when I look at it I can say 'I've earned that'.

Now ten series on what would be the souvenir you'd want to take away?

The Guide Dogs for the Blind spaniel model from outside the chemist - the gift shop which becomes the chemist shop in the series. It is one of those old models that you put money in to raise funds for the charity. It's owned by a prop house and is hired every time we film. Prop houses famously don't sell anything, so we will have to talk.

We have the Doc's car. We bought it, and although it is pretty old now it still looks great on camera.

What was it like to take part in the Platinum Jubilee celebration at the Royal Windsor Horse Show?

It was so lovely to see the reaction of the crowd to The Queen at the Platinum Jubilee Celebration at the Royal Windsor Horse Show. But you could also see that it was nice for The Queen. She was waving and leaning out to see people as she went round. She just loves the horses. The most poignant moment was when her own pony was led into the arena with a saddle on but no rider, and also when her granddaughter drove the Duke of Edinburgh's carriage into the arena.

What is next?

Next I am going back to the Pacific to explore more islands for a second documentary series, Islands of the Pacific for ITV - the first was shown earlier this year.

I've been asked to be president of the World Clydesdale Show in Aberdeen in October and I am going to take my two Clydesdales up with the carriage.