[rkangel]

This is called a Storage heater (https://en.wikipedia.org/wiki/Storage_heater), usually referred to in the UK as a Night Storage Heater as it took advantage of cheap electricity at night to provide heat for a house.

Fitting Night Storage radiators was a much cheaper way of fitting central heating than the normal boiler and plumbing approach, and when electricity was cheaper it made more sense. Now, it makes no sense and if you buy a house with it the first thing you have to do is put in "proper" central heating. But maybe with excess renewables that will swing back.