Partners father demanding repayment of gift

[Feiana]

My partners father loaned him some money about 6 years ago, father claims it was £7000 and then a few years later paid for my partner to do a training course, father claims this cost him £3000. My partner repaid his parents money each month for around 2 years and then his father told him to forget about the rest. After no contact for 2 years his father has messages him out of the blue demanding £10000 to repay his (fathers) mortgage as he wants to retire now and has not finished paying off his mortgage after taking out numerous remortgages to pay for holidays and cosmetic surgery after the date of the loan to my partner. There is no written documentation, the money was paid part by bank transfer and part was the fees for the course paid directly to the course company. Is there any legal way they can force my partner to pay this money back, as we cannot afford to pay this, especially as some was already paid...