The British Rail Class 357 "Electrostar" alternating current (AC) electric multiple units (EMU) were built by ADtranz, Derby (now owned by Bombardier Transportation) from 1999 to 2003 at a cost of approximately £350 million. The Electrostar family also includes Classes 375, 376, 377 and 378, and is the most numerous type of EMU built in the post-privatisation period of Britain's railways. These units were built in two batches for LTS Rail, since rebranded as c2c.