In February 2006, National Grid announced that it had agreed to buy KeySpan Corporation, a gas distributor and electricity producer in the United States, for $7.3bn (£4.1bn) in cash. Around the same time, National Grid also announced the acquisition of New England Gas Company, a Rhode Island subsidiary of Southern Union Company. The acquisitions of the two natural gas delivery companies doubled the size of National Grid's American subsidiary, creating the second largest utility in the United States with more than 8 million customers. The acquisition of KeySpan was completed on 24 August 2007, following government and regulatory approval and endorsement by the shareholders of the two companies. In May 2007, National Grid formed a joint venture with the Dutch transmission operator TenneT for a 1,000 MW BritNed DC link between the Isle of Grain in Kent and Maasvlakte, near Rotterdam. The installation of the first section of cable link started on 11 September 2009, and the entire cable was completed in October 2010. The interconnection became operational on 1 April 2011, and by January 2012, electricity flow had mostly been from the Netherlands to the United Kingdom. The BritNed interconnection would serve as a vital link for the foreseeable European super grid project. In the spring of 2011, National Grid sold off its services in New Hampshire, after their request to increase gas and electric rates was denied. In November 2015, it was announced that Steve Holliday, the CEO for ten years, would leave in March 2016 and that John Pettigrew, its executive director who joined National Grid twenty five years earlier, would succeed him. In June 2016, the Energy Select Committee argued that the company faced too many conflicts of interest, particularly with regard to its ownership of international interconnectors. The committee proposed that the company should be split up. In December 2016, National Grid agreed to sell a 61% stake in its gas distribution business to a consortium of Macquarie Infrastructure and Real Assets, Allianz Capital Partners, Hermes Investment Management, CIC Capital Corporation, Qatar Investment Authority, Dalmore Capital and Amber Infrastructure Limited, with a further 14% stake under negotiation. The sale was completed on 31 March 2017, following clearance by the European Commission, and the resulting company was named Cadent Gas. In July 2019, National Grid's Electricity System Operator arm, separately from its Electricity Transmission arm, announced its intent to join the Powering Past Coal Alliance, furthering its goal of becoming a zero carbon electricity system by 2025. At the time of its announcement, National Grid was the largest energy company based in the United Kingdom to join the alliance, according to publicly available 2018 financial figures.