This guy was the director of image processing at Reliance/Lowry between 2006 and 2010 and said that a 4k restoration was done during his tenure.
Some of the more notable projects completed during my tenure were Avatar, Prometheus, The Amazing Spiderman, The Social Network, The Girl with the Dragon Tattoo and The Curious Case of Benjamin Button. The Image Processing team completed 4K restorations of The Star Wars Trilogy and Titanic and 2K restorations of Alien, Aliens, Terminator, The Abyss and True Lies.