Crosstree Real Estate Partners, the London-based private real estate investment firm, has announced the achievement of a series of significant milestones at One Berkeley Street in London’s Mayfair, its landmark development comprising 60,000 sq ft of prime fully refurbished Grade A offices, 20,000 sq ft of flagship retail and F&B space on Piccadilly, and the 181-room ‘1 Hotel Mayfair’.