Sam Kay a.k.a The Ringer
Mr Kay, who told viewers he was studying chemistry, had already left to become an accountant at PricewaterhouseCoopers.
A BBC statement said: "The University Challenge rules on student eligibility are that students taking part must be registered at their university or college for the duration of the recording of the series. Whilst obviously not intending to, Corpus Christi broke this important rule where other universities and colleges taking part adhered to it. We therefore find ourselves in the regrettable position of having no choice but to disqualify Corpus Christi from the final."
Mr Kay said: "I hugely regret not confirming my change of status to the University Challenge programme makers before the final rounds. I had honestly believed I was eligible as I had indicated my course dates when I applied."
Oxford, led by Gail Trimble, romped to victory in the show last week. They came from behind to win the final by 275 points to 190. Gail has been dubbed the greatest University Challenge contestant ever, after she scored more points than her three-team mates combined in the run up to the final and appeared so untroubled by the questions that host Jeremy Paxman was prompted to exclaim: "My God, you're laughing because they are so easy!"
Gail Trimble a.k.a. the Human Google a.k.a. the Intellectual Blitzkrieg
This ruling means that the hard-fought title now goes to Manchester University.Manchester team captain, Matthew Yeo, said: "While we accept the decision of the judges, we are saddened to have been awarded the trophy under such circumstances."