Providing a wall, fence or gate does not obstruct the view of somebody using a highway or endanger a highway user, planning permission is not required adjacent to a highway used by vehicles for walls, fences and gates up to 1 metre high. In other locations they can be up 2 metres high. It should be noted that if a fence, wall or gate is to separate a property from an adjacent highway, even if it does not abut the highway directly, it can still be interpreted as having to be no more than a metre high. If you are proposing to erect a fence, wall or gate, to which this might apply, seek advice from your Planning Department. A fence, wall or gate around a listed building automatically requires planning permission.
Repairing or altering (but not replacing) a fence, wall or gate does not require permission, provided its height is not taken above these limits. Again this would not apply to listed buildings and planning permission would be required.
If the erection of the wall, gate or fence encloses an area of land which facilitates a change of use then planning permission will be required e.g. if you extend your fence into a neighbouring agricultural field then this would be a change of use from agricultural field to private garden. This would require planning permission even though the fence may not.