A 16-year-old boy has left a tunnel near Euston station which has been dug in protest against the HS2 rail project.
The teenager was removed on a stretcher having been underground for 22 days.
He is the fourth protester to leave the tunnels under Euston Square Gardens which are thought to be 100ft (30m) long.
HS2 Ltd said the teenager was going to be assessed by paramedics before being handed to the Met Police.
The network of tunnels, which were dug in secret by HS2 Rebellion protesters, were discovered on 26 January.
The boy was the youngest person taking part in the demonstration.
Some protesters remain underground, while Scott Breen, 46, Lazer Sandford, 20 and a 17-year-old girl have all been arrested after leaving.
Both Mr Sandford and the teenage girl had previous bail conditions updated requiring them not to interfere with any HS2 site when they appeared at Highbury Magistrates’ Court on 9 February.
Mr Breen, the third tunnel protester to be arrested, has been ordered to appear at Uxbridge Magistrates’ Court on 26 February for allegedly breaching a community order.
The campaigners last week lost a High Court bid to block an operation to remove them.
A HS2 spokeswoman said safety of the protesters, staff and emergency services remains of “paramount importance”.
She added: “We continue to do all we can to end this illegal action safely, and we reiterate our message to those underground to comply with the court order and exit the tunnel immediately – for their own safety.”