SAS officers warn that Britain is unprepared for a Mumbai-style attack
Two former senior commanders of the SAS have warned that Britain's security forces would be unable to cope with a Mumbai-style terrorist attack in central London.

This would temporarily create a war zone within London and one that cannot effectively be countered by the police alone. The police are good at policing but we doubt they would want to try war fighting.
Link:http://www.telegraph.co.uk/news/ukne...le-attack.html