British police have tightened security at Westminster amid fears of an IRA bomb attack in advance of a general election due in the next few months.
"The Palace of Westminster remains at a high level of threat from the Provisional IRA," parliament's security chief Mr Peter Jennings told the 4,000 staff.
"The IRA will be keen to gather whatever targeting information it can, especially concerning our security measures, including closed circuit TV coverage, access arrangements and patrols," he said in a letter quoted by the Times newspaper.
Access restrictions have now been imposed, passholders face random checks and bag searches are being intensified.