They say you should be careful what you wish for and anyone living in the St Giles Rookery in London, and hoping for free beer, were probably saying that loudly and repeatedly on 17 October 1814 when an enormous vat at a local brewery burst engulfing the whole area in over a hundred thousand gallons of ale. For sure that they didn't mean to be washed out by a beer wave...
More information:
independent.com/the-london-beer-flood