Metal thieves have been warned Sutton is a "no-go area" as police and the council have pledged to make use of new laws.
A new act means scrap dealers and salvage operators must apply for a licence from Sutton Council and keep records of who they buy from.
The Scrap Metal Dealers Act 2013 also bans cash purchases meaning all scrap metal transactions must be made by cheque or electronic transfer.
The new law is aimed at stopping metal thefts that have affected railways, schools, churches and even plaques from war memorials.
Previously, people who sold metals to scrap dealers were virtually untraceable.
Now the new law has come into effect, both Sutton police and the council have pledged to use all the powers at their disposal.
Chief Inspector Neil Tyre, who is the lead officer for metal theft at Sutton police station, said his team will be "relentless" in enforcing the law while Sergeant Jon Eames, who has been running enforcement operations, added: "Our message is simple: get licensed or get caught - with unlicensed dealers risking losing a day's load of work and a whole lot more besides."
Councillor Ruth Dombey, leader of the council, said: "We will use the new law to make Sutton a no-go area for metal thieves.
"It's important that legitimate businesses obtain the appropriate licence if they buy or sell scrap metal in the borough.
"Metal theft is unfair on those who have to cover the costs of the damage caused to our schools, churches, homes and monuments. By working with the police we will crackdown on this criminal activity."
If anyone witnesses metal being stolen they should call 999 immediately. If you have any other information about metal theft you can call police on 101 or the charity Crimestoppers on 0800 555 111.
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