 These changes include, at Primrose Hill, in north London, moving the tunnel further north, and in west London reducing the width of the "Northolt Corridor"; lowering the alignment and creating a green tunnel in Buckinghamshire at South Heath; at nearby Amersham, where two footpaths would otherwise be severed, at Chipping Warden in Northamptonshire and Burton Green in Warwickshire, "green bridges" would be constructed; the alignment would be moved away from the settlements of Brackley, in Northamptonshire, Ladbroke and Stoneleigh in Warwickshire and Lichfield in southern Staffordshire, and from the Grade I listed buildings Hartwell House in Buckinghamshire and Edgcote House in Northamptonshire.In January 2012 the Transport Secretary announced further revisions to the Phase One route.The key revisions included a new tunnel at South Ruislip avoiding the Chiltern Line and mitigating the impact in the Ruislip area; realignment of the route and extension of the continuous tunnel, originally from the M25 to Amersham, to near Little Missenden; at Wendover and nearby South Heath extension to the green tunnels to reduce impact on local communities; an extension to the green tunnel beside Chipping Warden and Aston Le Walls; and realignment to avoid heritage sites around Edgcote.