5 Hanover Square Mayfair W1S Timeline News and progress updates from 5 Hanover Square new development in Mayfair W1S Post a new milestone Mitsui Fudosan, and its development partner Stanhope, have signed Helical Bar and BlueMountain Capital as new tenants at 5 Hanover Square, leaving one floor remaining to... 20/02/2014 by Buildington New website for 5 Hanover Square development can be found at www.fivehanoversquare.com. 01/01/2013 by Buildington New photos! 01/02/2012 by Buildington