UK Home Office Statistical Bulletin, 13 May 09:

Statistics on Terrorism Arrests and Outcomes Great Britain 11 September 2001 to 31 March 2008
For the period between the start of the data collection on 11 September 2001 to 31 March 2008 there were 1,471 terrorism arrests. This excludes 38 arrests made between the introduction of the Terrorism Act 2000 on 19 February 2001 and 11 September 2001 and 119 stops at Scottish ports under Schedule 7 of the Terrorism Act 2000.....