On 23 August 2008 a new feature, "Series Stacking", was announced. This feature was rolled out on 13 September 2008 and allowed viewers to watch previous programmes from selected series until the series had ended, with a limit of thirteen weeks after first broadcast. Not all programmes will form part of the stack, however. The BBC Trust permitted 15% of content to be offered as part of the stacking service; soaps, news bulletins and review-based programmes will not be stacked, nor programmes containing material of a legal nature, such as "Crimewatch".