Girls Aloud released their debut album "Sound of the Underground" in May 2003, which entered the charts at number two and was certified platinum by the British Phonographic Industry (BPI) later the same year. Their singles "I'll Stand by You", "Walk This Way", and "The Promise" charted at number one. Two of their albums reached the top of the UK Albums Chart: their greatest hits album "The Sound of Girls Aloud" and 2008's "Out of Control", both of which entered the chart at number one, with over one million copies of the former being sold.