Break-ins at two Hindu temples in the week following Diwali were carried out by the same person, police believe.
Religious idols and donations were stolen during the burglaries in Harrow and Brent on 9 and 13 November.
The Met said the timing, proximity of the buildings and method used to enter suggested both raids could be linked.
An image of the suspect, captured on one temples' CCTV system, has been released. Police have appealed for information.
In the early hours of 9 November, priests at the Shree Swaminarayan Temple in Willesden Lane spotted a man in the building when they were awoken by a crashing sound.
Idols and charitable donations made during the Diwali celebrations had been taken.
Four days later, the Shri Kutch Satsang Swaminarayan Temple (SKSS) in Westfield Lane was broken into at about 03:45 GMT.
Again, no suspect was found but CCTV showed a lone male searching the building where several items were taken.
In both cases the suspect forced entry into the building through a glass door or window.
Det Con Pete Wallace called on the community "to keep a look out for religious idols that may be offered for sale" and urged other temples to take extra care when locking away valuable items.