Engineers discovered a mystery Second World War air raid shelter while planning a sewer upgrade in Tottenham.
Now Thames Water is calling for anyone who has memories of it to come forward.
The engineers were working in Tariff Road when they came across the 70-year old shelter buried less than a metre below what is now the driveway for an industrial area.
The structure, which is 10m long, 2.5m wide and 2m high, can only be accessed via manholes.
The proposed route of the new sewer pipes has now been changed to preserve the shelter.
Mike Lang Hall, archaeological adviser to Thames Water contractors Optimise, said: “It wouldn’t have been right to demolish the shelter as it could have saved many lives during the war.
“Our project must go ahead to protect nearby properties from flooding but now we’re doing it in a way so as not to disturb such a precious piece of our heritage.
"There’s no record of ownership but we suspect it was built to serve the local community and possibly workers at the nearby Triumph factory."
Mr Hall believes it may have been built to serve the local community and possibly workers at the nearby Triumph motorcycle factory.
Anyone with information should email email@example.com or calling 0203 577 7700.