The UK Anti-Terrorism, Crime and Security Act 2001 was introduced in response to the attacks of 11 September. The act facilitates the use of electronic surveillance in order to prevent, detect or prosecute the perpetrators of terrorism, augmenting existing surveillance powers under the Regulation of Investigatory Powers Act 2000. This article plots the relationship between the two statutes and also their relationship to data protection laws. For example, the study explains that 'one way or the other, many more terabytes of data will have to be stored' by communications service providers about their users 'as a result of the threat or operation of Part XI' of the Anti-Terrorism, Crime and Security Act even though there are serious doubts as to 'whether Part XI will achieve its ultimate objective of providing evidence against nefarious activities.'

Anti-Terrorism Laws and Data Retention: War is over? by Clive Walker and Yaman Akdeniz, published in the Northern Ireland Legal Quarterly, 54(2), pp 159-182.
http://www.cyber-rights.org/documents/data_retention_article.pdf