Retro loaned the money (£500,000) to the marketing group on July 21 last year for three months, at an annual interest rate of 12%, with the interest payable in full at the end of the loan term.
It was extended for a further three months on October 21. The total sum due as at January 21 this year was £530,247.
British Virgin Islands registered Retro Grand is wholly-owned by the trustee of the Edward Trust, whose principal beneficiary is Edward George Morton.
The debt has now been converted into around 12.47mln Porta shares at £0.0425 per share and Retro Grand is now interested in around 5.69% of the Porta capital.