Caroline Catz, who has starred in Doc Martin since it began 18 years ago, playing the Doc's wife, Louisa Ellingham, narrates this insight into the making of the drama.

She says: "I want to let you in on some of the secrets of Doc Martin, and take you behind the scenes to meet the cast and crew to see just how we make the series. I have mixed feelings, as this is our very last series."

The documentary reveals how Doc Martin began, in 2004, following the film Saving Grace in which Martin Clunes starred as a GP, Dr Martin Bamford, but a very different character to the grumpy medic in the popular television series.

Footage from Saving Grace, and from the archives of the ten series of Doc Martin illustrate the journey of one of Britain's most popular dramas. Martin Clunes and the regular cast reminisce about the making of the drama, recalling their favourite memories

Martin explains how they made his character different from the doctor in Saving Grace: "We just struck with the thing of being wrong at every point. It's wrong to wear a suit in the sea. "It's wrong to drive a car that big in Cornwall."

Even the sets were designed to be at the wrong height for Martin so he constantly bumped his head.

Martin says: "I don't know why I haven't before, but I've enjoyed its success, and the way its caught on in the different countries and the feedback we've had has been really gratifying. But the word pride has only just popped into my little brain."

Dr Martin Scurr has been the consultant on the series from day one, helping the writers to pen all manner of strange ailments for the Doc to deal with. The former GP says some of the medical stories were cases that he had dealt with, and was frequently on set to advise on procedures, and pronunciations of complicated diagnoses.

Producer Philippa Braithwaite, who is married to Martin Clunes, says Martin often finds himself giving medical advice in real life - without even being asked.

"If someone is on antibiotics Martin will ask what they have been given, and we have to say to him' you are not a doctor'!" Philippa says.

She recounts the story of when they were in Paris a group of women were on segways and one had a nasty accident when she crashed into a wall.

"Martin turned into action man and went flying over to see if she was OK. She was semi-conscious, looked up at him and said 'It's Doc Martin'.

The show's production designers show how they transform the picturesque village of Port Isaac, in North Cornwall, into the world renowned fictional hamlet of Portwenn, and create the various scenes which challenge the Doc, with an array of stunts and special effects.

Doc Martin has millions of fans worldwide. Some of them have formed fan clubs which thrive on social media, including the Clunatics and the Bert Large Lovers Group. The dedicated organisers of the fan clubs arrange events during filming for the fans who have travelled from all over the world to catch a glimpse of the stars.

A farm just outside Port Isaac has been home to the production, with a former grain barn being transformed into a studio for interior scenes, and hay barns being used to park the numerous trailers for cast, hair and make-up, costume, and catering.

Selina Cadell, who plays pharmacist Mrs Tishell tells how her close friend and Hollywood star Sigourney Weaver came to have a guest role in the series. "Sigourney Weaver and I have known each other for 40 years plus and we're very, very close friends. She loves Doc Martin and was keen to be in it." But when Selina asked producer Philippa Braithwaite if Sigourney could be in Doc Martin she "sort of laughed and walked away."

Selina says: "And then Martin rang and said, 'Does Sigourney still want to be in it? Do you think she really meant it?' I said, "Yeah, of course. You should make it work."

Philippa explains: "So we wrote a part and then she wanted to come back and do it again and she was just delightful."

The documentary captures the poignant last day of filming on Doc Martin, as the cast and crew bid a fond farewell to Portwenn and to each other.

As Martin and Philippa walk around the empty sets which have been the Doc's home for 18 years, Philippa says: "It feels like demolishing your house - it's all over."