Flooding in the Dartford Tunnel which caused several hours of delays for drivers was caused by a failed water pump.
The flooding, which happened on Thursday afternoon, caused traffic to back up to the Swanley interchange, and led to huge rush-hour delays.
As a result of emergency works, the east-bore tunnel was closed. The second, smaller tunnel remained open but this did not stop traffic piling up.
The tunnel lets a certain amount of water in by design, which then gets pumped out - but one of the pumps failed on Thursday afternoon.
During the closure, the flooding was not actually on the road in the tunnel itself - but in a service section of the tunnel.
The tunnel was then closed in the interests of safety while emergency works were carried out.
A Highways England spokesman confirmed: "We had to close the east bore of the Dartford Tunnel [on Thursday] afternoon for emergency maintenance. We worked hard with our contractors to get the tunnel open again as soon as possible."
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