Yet, on paper at least, it is also home to Rowan Companies, one of the largest operators of drilling rigs in the world. In 2012, Rowan, which has a market value of $4 billion (£2.38 billion), shifted its legal and tax base from the United States to Britain. “We changed our corporate structure and we’re legally domiciled in the UK but our headquarters and our management team remain in the U.S.,” Suzanne Spera, Rowan’s Investor Relations Director said in a telephone interview from Houston. We take advantage of trying to be competitive with our effective tax rate.”