This one-off documentary is a gem. In the small hours of November 5, 1605, Guy Fawkes was found sitting underneath the House of Lords minding 36 barrels of gunpowder which he was anticipating would shortly blow King James I and everyone else in the building to Kingdom Come. We know of course that his fiendish plot was interrupted, and of the terrible price he and his fellow conspirators paid for their treason, but most of us don't know much more about the Gunpowder Plot, including if it could have succeeded, namely would a mere 36 barrels have been enough?

That last question is answered here in spectacular fashion as celebrating its 4th centenary, Richard Hammond and his team build an exact replica of the building in a secret location, and plant 36 barrels of gunpowder underneath it. If you are wondering how this was possible, one of the things you probably don't know is that the original House of Lords was a much smaller building than the spectacular Palace of Westminster you have doubtless seen on TV if not visited. The building was a mere 21 metres by 9, and the cellar was not really a cellar but an undercroft, ie the ground floor. Even so, this was a mighty task that involved using every single concrete truck in Cumbria and importing the gunpowder from Spain, a transport that had to be made under strict conditions of anonymity. The experiment was carried out on Army property.

It is, said Hammond, ironic that we set off fireworks to celebrate the big firework that didn't go off; that idea comes from the King who ordered as a public celebration of his deliverance from evil that bonfires be lit across the land. You can probably guess the result of the experiment, but if you get time, check out the video which was uploaded to YouTube last year.