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It's been euphemistically referred to as "mutually beneficial, transactional dating" but is the growing world of "sugar daddy" relationships just a sanitised term for sex work?

Freya is 22 and wearing jogging bottoms and a tatty T-shirt. She expresses herself unaffectedly and confidently.

She decided to start sleeping with older men for money while she was at university. "I love sex," says Freya. "And you know, I'm pretty good at it. So getting a sugar daddy - or two - was a no-brainer really."

Freya is one of a growing number of debt-ridden university students in the UK who have decided to become "sugar babies". These young women agree to be wined and dined by rich, older men who are known as "sugar daddies", in return for cash and gifts.

"My married sugar daddy gave me about £1,000 a night," says Freya reflectively. "He was just in it for the sex. My divorced sugar daddy gave me between £1,000 and £2,000 as an allowance."

I mean, yes, it's prostitution really but I think there's such a ridiculous stigma attached to that word Freya

Freya had worked hard to make ends meet at university. "I was working two jobs in my first year," she explains "It was awful - £5 an hour in bar work mainly and it was really affecting my studies. But this way, having my sugar daddies, I was able to concentrate 100% on my work and I got a First in the end. I mean, yes, it's prostitution really but I think there's such a ridiculous stigma attached to that word."

Despite acknowledging she was involved in sex work, Freya maintains she exercised a degree of control. "They were really attractive guys - I chose very carefully."

Freya's mother Mary agreed to be interviewed at the same time. She seems unfazed by her daughter's choice of career. "Actually I was quite proud of her," says Mary, shrugging. "I think it's a brave thing to do and I'm glad she wanted to discuss it with me. Of course my friends were all pretty aghast."

Money was tight for the family, Mary says. She was divorced and had other children to put through university too.

"As long as I felt that she was really happy and enjoying what she was doing, I couldn't see any problem with it and I thought it was a great solution," says Mary.

"All kids are born with talents. My daughter happens to have been born with beauty and sexual allure. It's like a commodity."

Find out more Emma Jane Kirby's report, Sugar Daddy, Sugar Baby will be broadcast on Radio 4 at 20:00 BST, on Monday 22 June Or listen on BBC iPlayer

Sugar dating websites are not supposed to be a conduit for selling sex - that would put them in a tricky legal area. But only the naive could get the wrong end of the stick.

"Enrol at Sugar Baby University today and get your education paid for by a generous sponsor," trills a soft female voice in one website advertisement.

Angela Jacob Bermudo is the PR director for the very same website. "I would not say sex is expected, I would say sex is aspired to," she says.

"A sugar baby gets financial stability with a monthly allowance," insists Bermudo. "And mentorship and a bevy of networking opportunities. In the UK, it's students who are our largest sugar baby demographic."

"It's the young ladies that actually have the power!" laughs 28-year-old sugar baby Alana.

"I'm the one with the power."

Image copyright ALAMY Image caption Some women are given high-value gifts as well as tuition fees

Alana sees the "sugar world" as a sort of Disney playground for adults. "I've lost count of the Louis Vuittons, oh and the holidays - New York, the Bahamas."

Alana currently says she has 13 sugar daddies on the go, but has had at least 40 over the years. Almost all the men are from a private equity or hedge fund background. She claims she has only ever slept with three of them.

"I always end up getting what I want," she says. "And that's the whole point of it. You've got to play the system. If you dangle the bone, they will keep coming."

She's now 28 and doesn't have a boyfriend.

I'm providing money to an individual who's decided they want a certain type of relationship Mike , "Sugar daddy"

"Sometimes you do get lonely. You're in late at night watching a movie and you might want company from someone. Not just any male friend but your partner, your boyfriend.

"But would that be good enough for me now? Would that be satisfying enough?"

Mike, who's 38 and who works in IT, says he doesn't have time to find love. So for the past three years he's opted for short cuts - sugar arrangements. He pays his current arrangee £2,000 a month, plus up to £1,000 a month shopping allowance. He has turned his back on traditional relationships.

"Been there, tried it, done it, got the T-shirt and the tears." He describes himself as single.

"I'm providing money to an individual who's decided they want a certain type of relationship. Expectations go both ways."

Mike is perfectly up front about expecting sex from any girl he's paying. He likes his arrangements to be monogamous and long-term. He speaks caringly about the girls he's had arrangements with.

"The most I've ever spent on an arrangement date was about £40,000," he says. "For a weekend."

Mike admits he has been disappointed by past arrangements where girls have been ungrateful. But he says he has never felt used.

"I look back at my parents. They're in their 70s now and have been married for over 50 years. To this day my dad still puts money in my mum's account each week. What's the difference?"

Catherine is a 21-year-old law student at a good university in the UK and once she's sat her finals, she intends to end her sugar arrangement.

She praises her sugar daddy Mark as "the kindest man on earth who literally respects my every decision". He has been paying her rent and tuition fees for the past year.

Catherine was clear from the start of their arrangement that she didn't want a physical relationship with Mark. But her resolve that the relationship should stay platonic floundered. "I felt so bad taking money and not giving back."

Shortly after Catherine agreed to a physical relationship, she saw her monthly arrangement fee rise from £700 to £1,200.

"He wants me to be a certain way. He wants me to do so many things for him, physically and mentally," she complains. "But he is so generous to me. You know, this is easy money."

Rachel , 21, knows the dangers. A timid language student at another top university, she joined a sugar website while she was still at school after hearing her parents arguing about money. She saw it as a "quick way of getting money for not really doing a lot".

He gave me £100 or so when we met for dinner and helped me to buy some text books Rachel

Her first sugar date ended brutally when the sugar daddy she'd agreed to meet drove her to a car park and tried to force himself on her.

But a need for money prompted her to try again.

For 18 months, Rachel saw a man in his late 50s. She never slept with him.

"He was single and quite old and didn't have any friends," she says. "He just wanted company because he was very lonely. He gave me £100 or so when we met for dinner and helped me to buy some text books."

Rachel broke off the arrangement, not because he was demanding more from her, but because she felt she was exploiting him. When she talks about it she is clearly holding back tears.

"I actually liked him as a person and I just felt I was taking advantage."

"I'm sure a lot of people on the site do treat it clinically and can just use people but I'm quite an emotional person. I was never approaching the site that way. I feel quite bad about taking it that far almost."

Emma Jane Kirby's report, Sugar Daddy, Sugar Baby will be broadcast on Radio 4 at 20:00 BST, on Monday 22 June - or listen on BBC iPlayer

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