A 16-year-old anti-HS2 campaigner arrested after leaving the network of tunnels near Euston Station has been released on bail, the Metropolitan Police said.

The teenage boy was the youngest protester on the site, and became the fourth person to leave the tunnels on Wednesday after 22 days underground.

He was handed over to police by bailiffs working for HS2 after being checked over by paramedics, a spokeswoman for the rail link said.

The Met said on Thursday evening: “A 16-year-old male who was arrested on suspicion of aggravated trespass on Wednesday, 17 February, has been bailed to return to a central London police station on a date in mid-March.”

The 100ft network of tunnels, which was dug in secret by protesters who object to the redevelopment of Euston Square Gardens in London as part of HS2, were discovered on January 26.

The protesters last week lost a High Court bid to block an operation to remove them.

Among those still underground is veteran environmental campaigner Dan Hooper, otherwise known as Swampy.

On Sunday night, protester Scott “Scotty” Breen, also known as Digger Down, left the tunnels and was escorted away by police.

The 46-year-old, from West Drayton, west London, will appear at Uxbridge Magistrates’ Court next week, accused of failing to comply with a community order.

Two other anti-HS2 campaigners who emerged from the tunnels earlier this month have had breach of bail proceedings brought against them for their role in the protest dropped.

Lachlan Sandford, 20, known as Lazer, was said to have breached bail conditions related to proceedings at Wycombe Magistrates’ Court in November.

A 17-year-old protester was accused of breaching bail conditions relating to court proceedings at St Albans Magistrates’ Court in December last year.

The charges against both were withdrawn.

But their bail conditions were amended barring them from interfering with the workings of any HS2 site and not to enter, be present, or remain in any HS2 site or building which is clearly identified as such by way of a sign, fence or other marking.