The Windscale reactor was the epitomy of early nuclear reactor design overconfidence and ignorance. It made Chernobyl, infamous for its lack of a containment dome, look like a model of safety.
Windscale's design entailed a tunnel filled with a big block of flammable graphite, heating the graphite to hundreds of degrees with nuclear reactions, and then cooling it by blowing fresh air (you know, full of oxygen) over the hot, flammable graphite. Yes, truly a safe concept.
Surely nothing could go wrong in a reactor lacking adequate numbers of thermocouples to monitor the core's temperature; having only a single shutdown system (the control rods); and lacking any passive safety features. The one bit of lipservice to safety - which most of the designers thought was a waste of money - was a filter on the hot air exhaust chimney. (And it worked extremely well, though it was only treating the symptoms after the reactor caught fire.)
And you're incorrect about its operation. Windscale was *only* meant to produce plutonium for bombs, and completely designed around that goal, with no provisions for, say, power production. Later, Britain tried to make it produce tritium for hydrogen bombs to keep up with the Americans, and that's where some of the trouble began - this began producing hotspots in the graphite.
I love nuclear power, especially modern reactor designs with their elegant, brilliant passive safety systems. But I cannot say anything good about Windscale's design except maybe, "it was simple and cheap."