Four years ago I lent my daughter and her husband several thousand pounds to be repaid in monthly instalments. After three months they split up and no further money has been paid. I am a widow and a pensioner, and I do need the money back.
The question is: does either of them have any money to pay you? If they don’t you may have to put it down to experience. If they do, a solicitors letter may prompt action but if that doesn’t work you may have to sue them for the money in the small claims court, producing evidence of the loan and of the repayments to date. There is no reason why you cannot claim the whole of the amount back from your ex son-in-law.