http://www.24dash.com/content/news/viewNews.php?navID=7&newsID=4369
"New powers to allow police to drug test people arrested for crimes such as burglary come into force in London. The new measures are part of the Drugs Act 2005, and will be used in those police areas with the highest rates of drug-related crime. For the first time, drug-misusing offenders will be tested on arrest for heroin and/or crack/cocaine for crimes such as street robbery and burglary. Those who test positive will be required to attend a compulsory drug assessment, even if they are not charged."
