On Monday, Four Corners investigates the secret tactics used by global chemical giant Monsanto, to protect its billion-dollar business and its star product, the weed killer, Roundup. When it was launched four decades ago, Roundup was hailed as a miracle product, a revolutionary herbicide that would transform farming and keep home gardeners happy too. And it came with the promise that it was safe. Now a landmark US court case has made headlines worldwide, with a jury declaring Roundup was a substantial factor in causing a school ground keeper's terminal cancer and that the company had failed to warn of the risk posed by the product.