British Land is pleased to announce it has exchanged on the sale of 12 superstores from its joint venture with Sainsbury's for £429m, representing a net initial yield of 5.0%, to Realty Income Corporation. Our share of the proceeds will be £193.5m1representing a modest premium to September 2018 book value.
This is the latest example of how we are delivering against our clear long-term strategy to build an increasingly mixed-use business focused on three core elements: campus focused London offices; a smaller, refocused Retail business and Residential, principally build to rent. As part of this, we expect Retail to comprise c.30-35% of the assets of our business, down from around half today.
Alongside investment into our campuses and progressing unique development opportunities such as Canada Water, we are focused on further sales of retail assets which are not aligned to our strategy and continue to make good progress. We have a clear view of the value of our assets and despite the clear challenges currently in the retail market, we remain opportunistic and proactive. As a result, we have exchanged or completed on nearly £1bn of retail assets sales (£646m our share) since April 2018 at an average yield of 5.7% on terms marginally ahead of book value. This activity has included the sale of Debenham's Clapham and the Spirit pubs portfolio.
Once the transaction completes, which is expected at the end of May, our superstores exposure will fall to 1.3% of our portfolio based on September 2018 valuations with 6 standalone stores remaining. Net proceeds to British Land are expected to be c.£95m following the repayment of debt and associated break costs.