It also depends if a building line is being infringed. Usually the limit infront of the building line is only 1 metre approx 3ft 3". Planning permission is often not needed for a fence. Usually 8ft (usually a 6ft panel and 2ft trellis) is the absolute maximum wherever it is on the property unless there are specific business premises or similar requiring specific fencing needs and permission is then needed.
it is 2m without planning permision as buildersmate has pointed out.
a loophole (or eggshell area) is that it can be 2 m from your side but that may make it even higher if the property to which the fence divides is on a lower ground level?