Filthy thieves are causing a drain on council resources after stealing thousands of pounds-worth of cast iron grates.
Harrow Council is calling on residents to help catch two men who have been levering 50kg grates from road verges and making off with them in a white van.
The thefts began at the start of June and have centred around Pinner and South Harrow, but officials fear the crime spree could spread.
Councillor Susan Hall, portfolio holder for environment services, said: "These thieves are currently stealing gully grates faster than we can replace them.
"Their selfish crime means that we have to cone off the areas affected and then cause extra disturbance when we replace them.
"We would appeal to anyone who sees suspicious activity around a grate to call us. These people are ultimately stealing from residents as Harrow Council is paying for the cost of replacements."
The council has been forced to fork out £15,000 for 50 replacement grates and has employed two full-time road crews to fit them.
It is suspected the stolen grates are being taken to unscrupulous scrap dealers where they can fetch around £125 per tonne.