Invista Foundation Property Trust Limited has exchanged unconditional contracts to sell its 21.6% share in the joint venture that owns Portman Square House, London W1 for £23.11 mln. The deal is part of the disposal of the entire long leasehold property interest. Completion of the transaction is expected on 31 March 2010. The company's share in the property currently produces a rental income of £1.9 mln per annum.