Just after your thoughts on something. If a multi is put on that has competitor dependency can the betting agency take back any winnings??

eg I placed a multi that is competitor dependent and it is accepted, it wins and the winnings are paid. Is there any chance in the future of the agency requiring the money to be paid back because they shouldnt have accepted the bet in the first place?? Or once they accept the bet and the event starts do they have to honour it, or could they just refund the initial outlay, but any previous winnings I am entitled to??

Most have there rules outlined in regards to all betting situations and this would be the best place to start.