I know a lot about “Sam”. I know that he is studying for A levels in English and drama, and that he was in a school play. I know which fee-paying school he attends and that he is on the rugby team. I also know that he is applying to university this year - because he has paid me to write his personal statement to help him to get there.

As the deadline approaches for students to apply to the Universities and Colleges Admissions Service (UCAS), some students might be tempted to pay organisations to carry out the work for them.

When bespoke essay-writing services first appeared on the internet four years ago, there was a flurry of righteous anger. Sites such as OxbridgeEssays.com promised to match students with writers. Schools and universities were outraged. Having problems with your English GCSE coursework? For £147, Oxbridge Essays will get an English graduate to write it for you. Need a PhD dissertation by the end of the week? That will be £6,000. Because the essays are unique, plagiarism was almost impossible to detect.

Sam's requirements - I don't know his real name - were for a personal statement for entrance to university on a media-related course. I put myself forward to Oxbridge Essays to write it for him - for a fee. Half an hour after my bid for the job a document from Sam himself arrives. It lists his likes (rugby, drama and socialising); his AS-level grades (a C average); his ambitions (“to create a media corporation”) and his views on journalistic ethics (“a journalist needs to have legal, moral and ethical responsibilities”).

My bid is accepted and by 6pm the next day I have to produce a 650-word personal statement. Of course, Sam has signed a contract promising not to use it for his university application. In return, I have signed a contract promising not to upload my document on to any external database. These would include the anti-plagiarism websites that could catch Sam out if he does. For the service, Sam paid Oxbridge Essays £150. I will get £10 of that.UCAS calls Oxbridge Essays disingenuous. Cambridge University has castigated it as “a deliberate attempt to undermine the academic integrity of this university”. But as the company's website stresses, these essays, which can cost thousands of pounds, are just “for inspiration”. So it is legally in the clear.

And Oxbridge Essays is flourishing. UCAS says that it does not believe such sites can be stopped: “It would be better if these sites did not exist, but while applicants are prepared to pay for what they believe is a better personal statement, these services will continue to be provided.”

Nottingham University tells me that if it knew a student had been to Oxbridge Essays it might affect his or her application. “All students are warned against using these types of websites,” it says.

In the six weeks of my investigation, I was sent 1,000 subjects for possible essays. Most were undergraduate level, but a sizeable minority - around 100 - were personal statements such as Sam's. He is applying for courses related to journalism and media studies, making me an odd choice: all Oxbridge Essays know is that I have a mathematics degree from Cambridge. The company's unique selling point is that all its essay writers come from Oxbridge, claiming that this gives it the ability to guarantee first-class essays. It is a claim that can never be challenged, as to do so would be an admission that you had used one. Later, one of its staff admits that, with essays, marks will always be subjective.

The company website boasts that: “The universities of Oxford and Cambridge are world famous as the greatest universities in the United Kingdom.” My good fortune to have done well in an interview a decade ago means that I have reached “the pinnacle of academic excellence”. All of which should make Philip Malamatinas, a Birmingham University graduate, feel a little inadequate. Malamatinas, 24, is the co-founder of Oxbridge Essays and, judging by the cut it takes from my work, he is doing rather well. “None of our work is plagiarised,” he tells me at a meeting at a hotel near his office. Why, then, will he not upload it on to anti-plagiarism websites? “Because we own the copyright.” He repeats both these phrases half a dozen times.

The frequently asked questions section of its website includes the queries: “Is this service totally confidential?”, “Will my written work be checked by my university for plagiarism?”, and three other similar questions. The answers would reassure people who did decide to plagiarise. I ask Malamatinas why he brings up plagiarism, if it isn't a problem. He responds with a bizarre analogy about suicides and paracetamol: chemists sell drugs, but it isn't their fault if people exceed the maximum dose.

Christopher Boadle, his colleague, outlines their moral case. “We are supplementing the teaching process - offering that extra layer of support to students who aren't getting it.” He says that Sam might be attending a failing school and it is sad that he cannot go to his teachers for help.

I seem to be with the only two people in the world who believe that these websites are not encouraging plagiarism. Their business model makes plagiarism undetectable and their ethical model relies on thousands of people - who know they cannot be caught - behaving with integrity. Ant Bagshaw, the Cambridge University Student Union education officer, has been campaigning against Oxbridge Essays for months. “These are factories to help people cheat,” he says. “If students are struggling to do essays, they need to speak to welfare services - not to essay sharks.”

Even for an impoverished student, spending much more than an hour and a half to earn £10 seems a poor deal. I try to be fast.

When writing my own personal statement, I agonised for weeks. I feel I have done a better job this time. But when I was 18, what I produced was not what was submitted in its raw form. It went through an exhaustive editing process - with tutors, the head of sixth form and even the headmaster making notes in the margin.

And that is the strange thing. Why did Sam bother? His parents pay a lot of money so that the school can help him with this kind of problem. Teachers with decades of experience in university entrance are available to tweak and advise.

Sam's school makes that point when I speak to it. It argues that there is no proof of plagiarism because no one knows if he submitted the Oxbridge Essay personal statement to UCAS. “You know, sometimes people get these as model answers, for inspiration,” its deputy head teacher says. It claims to be unable to identify Sam from the information that I provide.

Sam's education costs thousands a year. He can afford £150 for a personal statement but, according to his application, has never had a paying job. His work experience consists of placements in a family company and of shadowing a lawyer - it would not be a stretch to assume a family friend. Someone who is a family friend - Sam says so - is senior in a media company: surely a better qualification for journalism than media studies degrees.

Sam has every advantage, every contact, and he will do well. A century ago he would be assured of a place at Oxbridge. But, for one brief period in his life - one state-enforced moment of meritocracy - privilege was meant to be irrelevant. If he has used my personal statement, he has found a way to get around that.

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