If everything went according to plan, investors in Heathrow Airport Holdings Ltd., which owns and operates London’s Heathrow Airport as well as a number of other U.K. airports, would probably have expected the assets to exhibit characteristics typically associated with brownfield investments: lower risk, inflation protection and a large share of return generated from predictable cash income to help meet outgoing payment obligations.

But things do not always go to plan. Over the lifecycle of a long-term brownfield lease, such as the 99-year lease for Port Kembla and Port Botany in Australia, expansions may be required, regulations can change, and what appeared to be a stable, income-producing asset may suddenly require significant capital injection before desired returns can be met, essentially putting the asset on the front end of the J-curve just like a typical greenfield investment. This issue c