Police are urging residents to take security precautions after a spate of burglaries in the Wealdstone area earlier this week.
There were nearly 20 burglaries in one two-day period with offences mainly taking place in the daytime or early evening.
It is believed that small groups of two to three men have been knocking on doors to check whether houses are occupied, later gaining access to properties from the back.
They usually arrive empty-handed and use bags and suitcases they find in homes to carry away items including jewellery, laptops, mobile phones and cash.
To see the latest burglary prevention advice from the Metropolitan Police click here.
If you see anyone acting suspiciously then call 999.