Monaco court orders London businessman to pay his ex-fiancee one million euros he promised her before finding out she was a high class prostitute Dutch-born Robertus Thielen, 52, proposed to Russian call girl 2 years ago He gave her cheque as 'financial security' to be cashed after their marriage But he discovered 'Diana' was a high class call girl A Monaco court has now ordered Mr Thielen to honour the payment A wealthy London businessman has been ordered to pay one million euros to his ex-fiancee that he promised her before learning she was a prostitute. A Monaco court heard that Dutch-born Robertus Thielen, 52, proposed to the Russian call girl two years ago. He handed her a cheque worth £862,000 as 'unconditional financial security'. It was to be cashed after their marriage. A Monaco court has ordered a wealthy London businessman to pay one million euros to his ex-fiancee that he promised her before learning she was a prostitute But he discovered earlier this year that the 30-year-old, who was named only as Diana, was a high-class escort. The court heard she was selling sex in London, Moscow and the French Riviera - and that the wealthy property tycoon had even been paying for her flights as she jetted across Europe servicing her clients. Mr Thielen swiftly called off the engagement and demanded that she return gifts and jewellery including a £60,000 diamond engagement ring. His ex-lover refused, but when the one million euros cheque was bounced by Thielen's Monaco bank, the call girl took him to court to demand her money. The court heard she was selling sex in London, Moscow and the French Riviera (pictured) and that the wealthy property tycoon had even been paying for her flights as she jetted across Europe servicing her clients Thielen told the Monaco correctional court on Tuesday: 'As soon as I found out about her job, I broke off the engagement and demanded the return of the jewellery and the cheque.' But the prostitute told the judge: 'He told me the cheque was a guarantee of security to avoid having any kind of marriage contract, and we agreed I would cash it after we were married.' A prosecutor claimed: 'He knew perfectly well how she earned her money. There is no such thing on earth as a conditional cheque. Thielen, who was ordered to honour the cheque and pay a £860 fine, said after the hearing that he would appeal the ruling.