You may be in a difficult situation without a properly worded written contract, a verbal contract is, of course, as binding as a written contract, the difficulty comes with the terms of the contract being correctly remembered or if the matter goes to court proving the terms, particularly that it was a loan to be repaid and was not a gift. So you are relying on the memory of the debtor and assuming the solicitor was present as a friend rather than acting on your behalf, a friend. I think your best option would be to contact the friend who was present and ask them to write to the debtor and remind them of their responsibilities as your friend remembers them.