It's not owed to anyone if it wasn't a loan. However, if your wife is deliberately dissipating assets you can call her to account in financial proceedings. If necessary the father-in-law can be joined in proceedings as he is holding matrimonial assets in which you have a share.
Thanks Charles, wife solicitor has confirmed it is a loan.
Father-in-law submitted schedule of repayments, but, disclosed whereabouts half money loaned was returned, and remaining half used to pay off legal fees of wife, oh, and reclaimed costs of her car leasing costs (that he has paid)
It can be accepted that repayments have been returned to wife and spent..
But not accepted that they hidden lease costs or legal fees to offset loan and reduce capital assets available to share...