File on 4 exposes a multi-million pound global trade in fake diplomas. A complex network of online universities sells degrees, doctorates and professional qualifications - for a price. Some of the buyers have gone on to trade on these credentials, including them on their CVs and gaining jobs in public life. Others, after making an initial purchase, were blackmailed by the sellers, who threatened to expose them unless they paid out huge additional sums of money. Despite criminal investigations in numerous countries, why is there still a thriving trade in dubious qualifications and are institutions and companies taking the issue seriously enough? Reporter: Simon Cox Producers: Matthew Chapman and Helen Clifton Editor: Gail Champion.