Investors in premium London real estate can rest easy knowing that their tenants are among the world's wealthiest and stable renters. That's the approach that the UK Real Estate Fund operated by Schroders Plc, the venerable U.K. asset manager, has long taken. Listed among the tenants of its $3 billion worth of properties are the British government, Tata Steel and Lloyd's Bank.

But in the era of Brexit nothing is certain, especially traditional London real estate. So earlier this month the Schroders fund purchased five London-area self-storage facilities for $55 million, making it one of the first institutional investors in this decidedly low-prestige sector.

What the purchase lacks in cachet, it makes up in demographic logic. Downsizing retirees and the growing ranks of home renters in London are creating a chronic need for somewhere to put all their stuff. And that's creating what Schroders and other real-estate investors see as a Brexit-proof and recession-proof opportunity.