The Blackwall Tunnel had to be closed this morning after a jogger decided to run through it.
Police were forced to close the crossing for the man's safety after he was spotted on a CCTV camera feed.
He had been jogging through the northbound tunnel at about 2.20am.
Transport for London tweeted: "The northbound Blackwall Tunnel is closed due to a person who is jogging through the tunnel."
About 10 minutes later, it added: "The northbound Blackwall Tunnel has re-opened.
"Police are now having a word or two with the pedestrian..."
A spokeswoman for TfL said: "The tunnel reopened at 2.31am. Police attended and took the suspect away."
Scotland Yard has been contacted for a comment.
It comes less than two weeks after the tunnel was closed for 20 hours following a fuel spill from a crane lorry.
The incident meant the road had to be resurfaced at a cost of about £150,000.
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