Held – It was settled law that the general rule that costs should follow the event did not apply to family cases and that in cases involving children, in particular, costs awarded against one parent or another would be exceptional since the court would be anxious to avoid the situation where a parent might feel ‘punished’ by the other parent which would reduce co-operation between them. 

That would only impinge ultimately on the welfare of the child or children concerned. The conduct of the parties would, in reality, be the major consideration when deciding whether or not an exceptional order for costs should be made, and the ‘unreasonableness’ of conduct had to be relate to the conduct of the litigation rather than the welfare of the child. 

https://vlex.co.uk/vid/re-t-child-order-803425425