The lights blind me. I can feel the sweat dripping down my forehead. The cameras point at me like a pair of guns. Spare me please, I scream in my head. But it's all too late now. It's just too late.

"Cue," I hear through my earpiece. And, then, my punishment begins. "Hello, I'm Eleanor Harding. Welcome to QVC..."

I'm at the headquarters of the most successful shopping channel in the UK for an audition to become a guest presenter. The channel, based at Marco Polo House in Queenstown Road, has one million active customers, and is available in 21 million homes.

Competition is stiff. Many before me have tried and failed. Auditions take place once a week, and as many as 15 people can be seen in a day.

"Some of these people have never been on TV," guest coach Tina Halvorsen tells me.

"Once we had a lady who was so nervous she couldn't get any words out at all. She tried so hard, but she just couldn't do it. My heart went out to her."

I'm not doing much better. I look at the wrong camera for most of the time and my hand shakes as I try to enthuse about skin toner.

With two minutes to go, I've said pretty much all I'd prepared and I find myself clutching at straws. "Lovely texture - almost like coconut milk," I gush. Actually it doesn't feel anything like that at all.

Eleanor in action

By the end of the ordeal, I have acquired a new-found respect for those who do it every day.

Jill Franks has been a QVC presenter for 10 years, and she will often find herself presenting 15 products per hour.

"The key is to be calm," she says. "But you have to be outgoing, and you have to be a real person. The viewers are so passionate, and they're very intelligent. You have to be there on behalf of them, and give them the knowledge about the products they want."

Because QVC is a 24-hour channel, Jill can sometimes find herself working a shift starting at 5.30am.

"I'll drive in, then get myself showered and do my hair and makeup. Then I might meet the guests and organise what's coming up on the show. Every day is a challenge.

"I'll often take the products home with me so I know how to use them before the show. Research is key."

It sounds tough, but research can be glamourous. A presenter might find themselves flown to the Isle of Wight to research brand history. They might do a spot of filming at a craft fair in Las Vegas, or a gold fair in Verona.

Sometimes they'll even meet celebrities. Twiggy, Steve Redgrave and Patsy Palmer have all appreared as guests on QVC.

And when the cameras are off, the QVC team still have time for a little fun. You'll often find them kicking back at the Masons Arms, the Duchess or Dave's Diner, all in Battersea Park Road.

The palatial office in Battersea is just one part of the QVC global empire, and the products are sent out from a warehouse in Knowsley, near Liverpool. Although the company is set to move from Battersea in the next few years, nothing has been confirmed.

That's just as well, because expert guest presenters like myself are always needed on a one-off basis to talk about products.

These are often recruited from Wandsworth, so local gardeners, carpenters and electricians may all have a chance of appearing on the channel.

"Most of the full-time presenters are from a media background," says coach Tina.

"But the guest presenters can have other backgrounds. It's interesting because the ones that are quiet when we first meet them often turn out to be the best."

As for me, I haven't been called back for a second autition yet, but I'll keep practising. Just in case...