Woodmanafc

Hi all Our neighbour has had a wood burner for a couple of years but we have noticed that smoke comes into my sons bedroom as he like his window open. I have circled the flue in the image and my son’s bedroom is to the right of the flue. Can anybody tell me if the height of the flue is legal. It was part of an extension that went through full planning so I would expect it to be OK but I just wanted to check. Thanks in advance