Infrastructure can prove difficult to define, especially when you try to base a definition on the types of facilities that make up the asset class. A better approach for investors is to be clear on the types of returns they are seeking.

What is infrastructure? The answer if you are, for example, a civil engineer, might be pretty straightforward; infrastructure is the term for those structures that underpin civilization, the things we cannot do without — water treatment works, power stations, waste disposal facilities, roads and railways.

However, when you put the same question to four infrastructure fund managers, you may well receive five or six answers.

“People say, ‘infrastructure is infrastructure,’ but it is not all the same,” says Eric Melis, former Borealis vice president and founder of Pension Fund Infrastructure Advisors. “It is a very heterogeneous asset class.”