Dog insurance refusing to pay out after RTA - Help

[deanogtv]

Our 2 year old Lab was decently involved in an RTA which we was hoping our insurance we pay monthly would have covered, afraid not.
Here is why!!
Recently my 3year old daughter was playing in our garden and decided she would venture a little further and
figured out how to open our side gate. She had balanced on her bike next to the gate to reach the latch. Doing so she opened the gate ajar and our dog ran out past her and the accident happened out side of our house.
Now today we received letter explaining that the insurance company will next be paying due to our house and garden not being secure.
Now I fully appreciate they have these clauses but seriously. It really gets my back up that insurance companies constantly worm there way out of claims.

Should I try and defend this or take it from behind. I feel our 3 year old daughter wouldn't have know better and it was a pure accident she left this open not knowing the consequence of her action being only 3.

I know I'll get the usual, stop moaning a pay up, but if anyone has anything of value to add please do

Thanks