The MBSA was created by John Christopher Bowles to 'afford an asylum for the reception of aged and infirm members of Friendly Societies' who lived in or near London. Patrons were Queen Victoria and her mother, the Duchess of Kent. At first this was provided in houses rented for the purpose but once they had the funds they built the almshouses, designed by S. H. Ridley, with the Lord Mayor laying the foundation stone of the north block on 17 August 1836 (the Duchess's birthday) providing accomodation for 28 residents. In 1865-6 the side wings added homes for 64 couples. The west wing is named after Mary Ann Mackenzie who helped fund it. By WW2 the name had changed to Metropolitan Benefit Societies Almshouses. It is now a registered housing association.
The picture is from c.1863. All images that we have found show the building complete so we imagine the side wings were only delayed rather than not originally intended.