 It was used as a testing range for the Barnes Wallis's Grand Slam bomb and also the Bouncing bomb used by the Dambusters.The site was used to developed a more effective air-raid shelter, built over five and a half months at a cost of £250,000.Once complete, the site became the first anywhere in the world to be subjected to the devastating effect of Barnes Wallis's Grand Slam bomb, which was test-dropped on the site.