Britain is planning the biggest change to takeover rules in almost two decades. They could give the government new powers to block deals in all sectors of the economy to prevent homegrown companies in sensitive industries falling into foreign hands, Reuters reports. The existing rules are limited to large transactions. Business Minister Greg Clark wants to tighten the rules to cover all British companies, including small firms. The world’s fifth-largest economy has traditionally been one of the most open markets for global mergers and acquisitions.