Bristol City Council says "Some areas of Bristol are covered by Article 4 Directions. If your property is in one of these areas, you'll need planning permission for works that would normally be covered by permitted development rights". The directions that name boundaries are Cotham and Redland from 4 November 2012, Henleaze from 22 April 2021, Grove Wood at Blackberry Hill from 9 November 2009, Land at Sherrin Way from 26 July 1982 and Henbury from 1971. Their scope differs, and the address and the proposed work both have to be checked against the particular direction.
The Planning Portal, which governs the rule in Bristol, says you will not need to apply for planning permission to erect a new, or alter, maintain, improve or take down an existing fence, wall or gate if all of its conditions are met. Those conditions include that it is "next to a highway used by vehicles (or the footpath of such a highway) and it would not exceed one metre in height (from ground level)", or that "it would not exceed two metres in height (from ground level) if elsewhere", or that where one already exceeds those limits "its height would not be increased".
The Planning Portal also requires that "no part of the site is a listed building or within the curtilage of a listed building", that no part of the boundary "forms a boundary with a neighbouring listed building or its curtilage", and that "the right to put up or alter fences, walls and gates has not been removed by an article four direction or a planning condition". It adds that in a Bristol conservation area "you might need permission take down a fence, wall or gate".
In Bristol we would explain how you check the conservation boundary, any Article 4 direction and the proposed work before confirming whether permission is needed.