Boots UK Limited (formerly Boots the Chemists Limited), trading as Boots, is a pharmacy chain in the United Kingdom and Ireland, with outlets in most high streets, shopping centres and airport terminals. The company's former parent, The Boots Group PLC merged with Alliance UniChem in 2006 to form Alliance Boots. In 2007, Alliance Boots was bought by Kohlberg Kravis Roberts and Stefano Pessina, taking the company private, and moving its headquarters to Switzerland, the first ever FTSE 100 company bought by a private equity firm. In 2012, Walgreens bought a 45% stake Alliance Boots, with the option to buy the rest within three years. It exercised this option in 2014, and as a result Boots became a subsidiary of the new company, Walgreens Boots Alliance, on 31 December 2014.