The local authority are not in the habit of volunteering payment in circumstances like this. That is what they have said in their letter. However whilst they may not want to deal with the Ivy, they have a duty to do so if it grows from their land and it becomes a nuisance or trespasses. Just because they are the local authority, does not give them any immunity from that.
Your father could have cut any of the ivy off which went on to the fence but for some reason he didn’t do that. He is under a duty to mitigate his loss and he failed to do that. Hence, whilst the council are responsible for any damage caused by their failure to maintain the nuisance growth, they can argue that your father is partly to blame and hence, you should not recover the full cost of whatever the damage is. He did report it to the council would he did have the opportunity to remove the growth from his own side of the fence and he would be legally entitled to do that.
Under the Access to Neighbouring Land Act he would also be allowed to trespass onto the neighbouring land for any action required to preserve his own property.
As the council will not pay up you have no alternative but to take them to court to recover whatever this has cost you.
Whether you recover that or not will depend on the weight of evidence you have in support of your claim that if it were not for the Ivy, the fence would not have rotted. In that respect, you are going to need a letter from a fencing expert which confirms the posts have rotted and that they would not have rotted if it were not for the Ivy and that there are other posts with no Ivy which have not rotted. Without that evidence, your claim will fail.
It depends whether you want the trouble of going to court over this. The claim you say is for £1000 and therefore it would be Small Claims Court in any event. If you don’t want the trouble of going to court but still feel that the local authority are to blame, you can complain to the chief executive and if that doesn’t work, make a further complaint, to the Local Government Ombudsman. Complaints to the Woodsman are not dealt with quickly but at least they are cost and risk free.
Can I clarify anything for you?
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