 In 1951, after she had met Denis Thatcher and moved to Dartford, Margaret Hilda Roberts was employed as a research chemist at Cadby Hall on emulsifying ice cream.She later became the United Kingdom's first woman Prime Minister, Margaret Thatcher.By the late 1970s, J. Lyons & Co. began to decline as rapidly as it had expanded a century earlier, and in 1978 the company was taken over by Allied Breweries Ltd. Gradually, the Lyons infrastructure was sold off to pay for Allied's consolidation in the drinks industry, and the Cadby Hall complex was scaled down until the site was finally cleared in June 1983.