From Wikipedia: Rocksteady Studios is a British independent video game developer based in London. The studio is best known for Urban Chaos: Riot Response and Batman: Arkham Asylum.
Rocksteady Studios was founded in 2004 by Sefton Hill and Jamie Walker. The studio was recently acquired by Time Warner. Square Enix Europe (Eidos) has confirmed that it still retains a 25.1 percent stake in Rocksteady.