How tall can a Lego tower get?

There has been a burning debate on the social news website Reddit.
It's a trivial question you might think, but one the Open University's engineering department has - at the request of the BBC's More or Less programme - fired up its labs to try to answer.
"It's an exciting thing to do because it's an entirely new question and new questions are always interesting," says Dr Ian Johnston, an applied mathematician and lecturer in engineering.
Looking on the internet, he expected to find the answer, but was surprised to find only a lot of speculation.
Perhaps that's because not everyone who has pondered the question has ready access to a hydraulic testing machine, Kazinform quotes BBC News.
The 2x2 Lego brick looks vulnerable, placed on top of a metal plate, which a hydraulic ram is pushing upwards. On top of the brick is a second plate, with a load cell on top of it, measuring the force being exerted.
Safety glasses on, the engineers begin to nervously edge towards the door.
"We're setting it up automatically, so that we can all back out of the room, so none of us is in range when the thing goes bang," Johnston explains - positioned, I notice, slightly behind me.
And the load on top of the brick gets larger and larger. We reach 3,500 newtons (N) of force - the equivalent of having 350kg (770lbs) sitting on top of the brick - more than a third of a tonne.
The force climbs on, above 4,000N. And then...
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