EastEnders legend Pam St Clement will leave viewers open-mouthed as she smokes marijuana on TV.

The actress was filmed puffing away on a bong for the new ITV documentary Gone To Pot, which explores the use of cannabis for medical and recreational purposes.

The 75-year-old, who played soap icon Pat Butcher for 26 years, admitted she was doubled up in 'hysterics' minutes after inhaling the drug during a wild three-week tour around America.

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Pot Butcher: EastEnders legend Pam St Clement will leave viewers open-mouthed as she smokes marijuana on TV

Pam took a hit from the bong, which was being passed around the Puff Pass Paint Class, as she sat an at easel doing some painting.

She revealed: 'We were taken to this warehouse . . . there were easels, tables and chairs. We jumped in with both feet and sat down and started to paint this cactus.

'The guy came round with this joint and I took a puff, and [dart player Bobby George] took a puff then we got on with this painting. I thought, 'Oh well this a terrible painting and I don't know what to do with it'. I made it into an alien in the end. It wasn't a cactus at all.'

The actress, who admitted she had smoked marijuana before in her youth, said she and fellow celebrity ended up on the floor laughing after taking a puff.

Light it up: Pam looked slightly apprehensive as a new friend passed her the bong

She told The Sun newspaper: 'This person came along with a glass bowl thing with a pipe and a stem with an open top, like a mini bong, it was very delicate and she gave it to Linda then to me and she said, 'Take a puff'.

'So I took a puff and she said, 'Oh that's enough, that's enough' and I thought, 'Oh my God, this must be powerful'. I passed it on to Bobby and within five to ten minutes me and Bobby were virtually on the floor laughing it was so funny.

'I love it when you get the giggles when you shouldn't. It's wonderful -- just crying we were - so refreshing to do that, it really is."

Although more accustomed to chandelier earrings and drama on-screen, the actress immersed herself in the world of weed for three weeks in a road trip around America to understand the uses of marijuana - as well as meet people who have experienced the pros and cons of it.

Asked how she thinks people will react to seeing her smoke cannabis when the series airs next week, she joked: 'The youngsters will be like, "What?" I think my street cred will improve.'

New horizons: The actress was filmed puffing away on a bong for the new ITV documentary Gone To Pot, which explores the use of cannabis for medical and recreational purposes

Experimental: The 75-year-old, who played soap icon Pat Butcher for 26 years, admitted she was doubled up in 'hysterics' minutes after inhaling the drug during a wild three-week tour around America

She was joined on the trip by Loose Women's Linda Robson, 59, Christopher Biggins, 68, retired footballer John Fashanu, 55, and darts supremo Bobby George, 71.

Pam said the group were like 'kids at Disneyland' as they smoked joints and ate marijuana-laced meals.

They had their taste of weed at a hippy party in San Francisco on the first night of the trip.

'It was like going back in a time capsule to the 1960s. I didn't think that still existed, that hippydom,' St Clement admitted.

'The five of us looked so out of place it was unbelievable. These two guys were banging on the bongos and Harry, who had invited us, was there absolutely off his face.'

Confused: The actress, who admitted she had smoked marijuana before in her youth, said she was baffled by the bong and had 'never seen anything like it'. Pictured on EastEnders in 2011

New series: The actress immersed herself in the world of weed for three weeks in a road trip around America to understand the uses of marijuana - as well as meet people who have experienced the pros and cons of it

She said when a joint was passed to them, she and Linda exchanged glances and decided it would be 'rude to refuse'.

The soap star, who left EastEnders in 2012, said the drug gave them the 'wonderment of children', but she wanted to know more about the pros and cons of it.

The issue of legalisation has long been the subject of debate in the UK with marijuana having been reported to ease symptoms of arthritis, epilepsy, multiple sclerosis and several other conditions.

However, it remains the most commonly used and trafficked illicit drug in the world and evidence suggests that frequent and prolonged use can be detrimental to both mental and physical health.

Each of the five celebrities have their own reasons for exploring the issue - Pam has polymyalgia rheumatica and has had a knee replacement.

Weed adventures: She was joined on the trip by Loose Women's Linda Robson, 59, Christopher Biggins, 68, retired footballer John Fashanu, 55, and darts supremo Bobby George, 71

Documentary: Each of the celebs have their own reasons for investigating marijuana. Linda (pictured) is going through the menopause and gets hot flushes and mood swings

Linda is going through the menopause and gets hot flushes and mood swings, Fashanu is developing arthritis in his knee and Biggins has pain in his hip and back.

Meanwhile, Bobby broke his back, has had a new hip and knee, has had arthritis in his right hand and has had three toes cut off.

The celebrities begin their three-week voyage of discovery in San Francisco where the city is celebrating the 50th anniversary of the Summer of Love.

After a consultation over Skype with a doctor during which they list their health concerns, they are each given a medical certificate, which allows them to legally buy marijuana at a special dispensary.

Pam is now throwing her support behind the legalisation of marijuana because of how it helped two of her friends cope with the pain of multiple sclerosis.

Wild: Pam said the group were like 'kids at Disneyland' as they smoked joints and ate marijuana-laced meals. Pictured, Christopher Biggins

'I have two friends who both suffer from MS – they were forced into growing their own because they couldn't get any relief any other way,' she told OK! magazine.

'You shouldn't have to be forced to break the law, but when you're desperate what are you going to do? The only way to control it, I presume, is to make it legal.'

During their American travels, the group head out to meet the ‘Sisters of the Valley’, a group of women living a lifestyle based on the spiritual beliefs of a thirteenth century order called ‘The Begins’.

Their purpose is to rescue others from poverty and they live on a farm where they grow marijuana and make products from it including oils, salves and soaps.

Their products are made out of the non-psychoactive compound of marijuana, Cannabidol, also known as CBD - which won’t make you high, but the same can't be said about the type of marijuana the Sisters smoke.

Exciting: The celebrities begin their three-week voyage of discovery in San Francisco where the city is celebrating the 50th anniversary of the Summer of Love. Pictured, Bobby George

Struggling: Bobby broke his back, has had a new hip and knee, has had arthritis in his right hand and has had three toes cut off

Pam and Bobby have a few puffs of a joint - and Bobby compares the effects to having drunk four and half pints.

Fashanu has never taken drugs or had an alcoholic drink in his life and decides to start with a medicated CBD massage from one of the Nuns. He admits that meeting the nuns has been an eye opener.

Finally, the group head down Route 101 to Surfer’s Paradise in Santa Cruz, to meet marijuana master chef, 94-year-old Nonna Marijuana.

Nonna has been cooking with marijuana for the past five years after her daughter, Val, discovered it eased the seizures she suffered after a road traffic accident.

Hard times: John Fashanu, who has never taken drugs or had an alcoholic drink in his life, has developed arthritis

Val has since set up a charity to help others and the pair have cooked medicated food for patients with a wide variety of illnesses including AIDS, cancer, brain tumours and epilepsy.

The group get to eat the drug, which is metabolised differently to when it is smoked - with the effects taking two hours to be felt.

Nonna makes a variety of dishes, which include the pièce de résistance, marijuana ice-cream.

Christopher and Bobby in particular develop a taste for her Italian cuisine with its special ingredient. Pam also comments that they have 'pushed the boat out'.

Gone To Pot American Road Trip will start on Monday, November 13 at 9pm on ITV.