The Turbostar was the first new train type to be introduced after the privatisation of British Rail , and is the most common type of diesel multiple unit ( its electrical variant , the Electrostar , is the most common electric multiple unit ) . The Turbostar was the first new train type to be introduced after the privatisation of British Rail , and is the most common type of diesel multiple unit ( its electrical variant , the Electrostar , is in turn the most common electric multiple unit ) .