A Charedi father must demolish his family home after losing a planning dispute with a council.
Jacob Dreyfuss, president of Stamford Hill's Stolin-Karlin synagogue, rebuilt his two-storey home without planning permission, to add a cellar and a loft extension.
Hackney Council issued an enforcement notice and he appealed against it without success.
The government's Planning Inspectorate has now given him a year to "remove the unauthorised house".
Mr Dreyfuss was unavailable for comment this week. But if he fails to comply with the ruling, he could face criminal prosecution and ultimately a fine.
Last month the Planning Inspectorate heard details of the nine-year row between Mr Dreyfuss and the council over extensions at his home in Lingwood Road, Stamford Hill.
Planning permission had been granted in 2002, but Mr Dreyfuss extensively rebuilt the house, "substantially enlarging" on the plans accepted.
Council officers claimed the roof extensions were an "excessively bulky and obtrusive development" and did not fit with others in the street.
Mr Dreyfuss can now apply for new permission and alter the property to bring it in line with council rules. But he can only challenge the Inspectorate's decision if he believes an error has been made in law.
Cllr Guy Nicholson, Cabinet Member for Regeneration, said: "Hackney is sending out a clear message. If people choose to ignore these laws, we will take whatever action is necessary to deal with the issue."