Other problems included unclear billing, making it difficult to work out whether heating costs were fair or accurate, and poor customer service and complaints handling, with many having no access to Ombudsman schemes or independent redress if things go wrong.

One such disgruntled district-heating scheme user, living in Bow, explains he and fellow residents faced problems with the communal pipework silting up, meaning on occasion there wasn’t sufficient heat available and some problems using the controls — “which are unnecessarily complicated”.

But the real surprise was the cost.

“A communal-heating system is meant to be more efficient that individual systems, and our flats are heavily insulated with a clever ventilation system too,” the building-services engineer, who wanted to remain anonymous, explains.

“The radiators are tiny as the flat doesn’t need much heat to keep it warm. So you’d expect the monthly heating cost to be relatively low, yet it’s been £69 a month in our three-bedroom flat over the winter — more than our previous, flat which was almost 100 years old, and had an inefficient, old boiler.

“On top of that we pay a huge, monthly heating standing charge of more than £500 a year, which covers the cost of plant maintenance and future replacement. And with such well-insulated buildings, some have had to install air conditioning to cool down their overheating flats.

“Our windows are so small — to stop heat escaping — that we have to have some of the lights on even in the middle of the day. I’m fairly sure this more than offsets the heating savings.”