Cameron Bell, a curriculum leader and construction lecturer at Ayr College, got his first taste of life as an extra in 1986, driving a horse and carriage in the STV period drama The Campbells. He had to wear a wig, fake sideburns and look miserable.

“It wasn’t hard,” he confesses. “We were outside and it was a freezing November day.”

His next foray into film didn’t occur until almost 20 years later, when he was looking for something to do in the holidays and his wife suggested signing up to an agency.

“There’s only so many times you can cut the grass,” he points out.

Now he has racked up considerable experience as a supporting artist working on Scottish detective series such as Rebus and Taggart.

One of his best moments working on the latter came last year, filming in Dunure. Naturally there had been a murder - a mutilated body was discovered on a remote island. Cameron was playing the uniformed police officer escorting the body back by boat to the mainland. “It was beautiful weather and I was on the boat with Alex Norton, John Mitchie, Colin McCredie and Blythe Duff. It’s just good to get a chat with these people.”

Cameron, however, does not let rubbing shoulders with the stars of the small screen go to his head. He compares extras to trees - they are just background to decorate the scene, he says.

“If an extra is noticed, you’re not doing your job. You can’t kid yourself that you are Brad Pitt - they want ordinary, or even less than ordinary-looking people. They want you to just blend into the background.”

While Cameron is prepared to admit to having an ordinary face, there are limits. Last October he was told the BBC were “picking faces” for a role in kung-fu comedy Phoo Action and he had been chosen from his agency’s website.

“I was chuffed I had been chosen to do it. There were half a dozen of us, the director came up and said: ‘OK you six are going to be at an AA meeting.’ Obviously I look like an alcoholic!”

The biggest project Cameron has worked on is the film Doomsday, which went on world-wide release earlier this year and was directed by Neil Marshall, whose previous offerings have included Dog Soldiers and The Descent.

“What gets me with filming is the level of detail. It was a huge crowd scene. We spent three days shooting, had to go for costume fittings and have our faces made up to look really grubby and on screen the shot lasted for a minute.”

Cameron’s only speaking part was in the film Bon Voyage, which toured international film festivals but was never released. His role was as an Italian chauffeur for a glamorous country and western singer, played by Jenny Ryan, alias Tina Hunter in the BBC soap River City. He had to say “prego”, Italian for “you are welcome”, as she stepped out the car.

“I didn’t even get to speak English,” he says laughing.

Nevertheless, Cameron has been the star of the show on one occasion. Last year, he was involved in a production for Channel 4 called Rescue Remedies, a series of short films about alternative remedies for health problems such as impotence and hair loss.

Thankfully, he was involved in the episode about the common cold. But this still required a degree of embarrassment when he had to act out alleged cures such as sucking the air out of a hairdryer, wearing a pair of dry socks over a pair of wet socks in bed and having a mustard footbath.

“Mustard doesn’t show in water, so they actually used turmeric. Only problem with that is it’s a dye, so I had yellow feet for a week.”

Unlike Ricky Gervais in the comedy series Extras, Cameron does not see being a “supporting artist” as a step on the road to stardom. In fact, being an extra gives you an insight into the less glamorous side of acting, he says. “There are huge demands placed on people in the industry: they work 12-hour days and have to do night shoots. The actors on Taggart can work from 3pm until 2am and they are moving from location to location, living in caravans.”

Being an extra can be a little dull, he admits.

“There’s a lot of hanging about; sometimes you’re not even used. I’ve seen me drive from Ayr, arrive in Edinburgh for filming at 7am and never be used. But that’s rare - usually they’ll want you for something.”

What’s more, the money barely covers your expenses, he says. But it is getting the insight into the film-making process, meeting new people and the food that keep him coming back.

“The food is tremendous - you get worse food eating out in nice restaurants.”

Also, life as an extra is something totally different from his day-to-day life.

“Life is pretty intense in the college; I’m trying to control lots of different elements - I have staff to manage and of course students in class. This is the opposite: someone is telling me what to do - stand there, go there - it’s brilliant. I just take my iPod and my book, hang about and meet nice people.”

Cameron does, however, harbour one ambition when it comes to his work as a supporting artist: to be an extra on Dr Who.

If they are ever filming in Scotland it would be an honour, he says, to use all the experience he has garnered over the years, make himself as inconspicuous as possible, and blend beautifully into the background, as “man in pub” or “passer-by”.