My neighbours property is separated from mine by a 4 foot brick wall which goes to the end of our gardens.The properties are on a similar level but at the start of the gardens at the rear of our properties the level alters and my neighbour is then about 4 foot higher than me.He has now started to install a 6ft fence on his side which on my side towers nearly 10 ft,is this allowed has I was led to believe a fence should not be higher than 6 ft.