Drivers are being warned by police after a series of thefts of catalytic converters from vehicles in the borough.
Officers in Harrow are raising awareness among vehicle owners after thieves appeared to be targeting cars and vans in the area for the parts.
The three thefts took place in Margaret's Avenue and Sherwood Road in South Harrow and Blenheim Road in North Harrow.
Police say thieves have been targeting people carriers, 4x4s and commercial vans because of their high ground clearance, giving them easy access to the underside of the vehicle.
Catalytic converters are sold for their scrap metal value but thieves can only get a small amount of money.
Sergeant Jamie Kay from Harrow Police said: "Harrow is one of the safest boroughs in London and we want to ensure that our communities are and their property is not targeted by catalytic converter thieves.
"Accordingly, we urge vehicle owners to be vigilant and consider adopting some measures to help protect their vehicle against this type of theft.
"By working together, we can continue to make Harrow even safer."
Measures recommended by police include defensive parking, catalytic converter protective sleeves and security lighting.