Northwood is an elevated residential settlement in the London Borough of Hillingdon adjoining Ruislip Woods National Nature Reserve ( which contains the Ruislip Lido ) .
Which shares a northern border with Hertfordshire .
Northwood is an elevated residential settlement in the London Borough of Hillingdon adjoining Ruislip Woods National Nature Reserve ( which contains the Ruislip Lido ) and which shares a northern border with Hertfordshire .