Amusing footage has emerged showing what happens when you boil lager in a kettle.The video, captured at a home in London, shows foam building up inside the transparent kettle then coming out in bursts."At my friend's birthday on Friday we'd had a few beers, and pondered what would happen if we popped a few cans of Budweiser into the kettle," the filmer wrote online."On the Saturday after a few Rum and Cokes we decided to give it a whirl..."