Water from a burst main in Porlock Avenue, South Harrow flooded surrounding roads and caused severe delays to traffic on Wednesday afternoon (May 9).
Harrow police urged motorists to "find an alternative route" and the warned of "significant delays" as Affinity Water worked to fix the main at around 1pm.
Harrow Community First Response team tweeted a photo from the scene which shows flood water filling the road.
It wrote: "Harrow C Team are on scene at Porlock Avenue, South Harrow where a water main has burst. There are significant delays whilst Affinity Water conduct repairs. Please find an alternative route."
Whitmore High School in Porlock Avenue avenue has not been affected by the flooding.
A Whitmore School spokesman said: "The school is not affected by the flooding and is running as normal."
Harrow resident, Ajay Shah said: "The school is not affected but as engineers are on site, there's very slow moving traffic.
"There's lots of flooding just on the main road."
An Affinity Water spokesperson said: "We are sorry for any inconvenience caused by a burst water main on Porlock Avenue, South Harrow.
"Our technicians are currently working on site to carry out the repairs to the water main.
"To ensure the safety of members of the public and our technicians carrying out this work, we have traffic management in place and would like to thank everyone for their patience whilst this work is carried out."