Terracotta eco-warrior

The man jumped barriers to place the masks bearing the slogan "CO2 emission polluter" on two of the life-sized figures to highlight China's poor pollution record.

Security guards intervened after they were alerted by other visitors.

Martin Wyness, 49, was dragged away from the 2,200-year-old exhibits and has been banned for life from visiting the museum.

A Chinese official who travelled with the exhibits was inspecting the soldiers to see if they have been damaged.

Security has now been stepped up but Mr Wyness, 49, said he had no regrets about his actions yesterday. "I did it because I have got two children and I am very, very concerned about the global inaction over climate change, particularly what is happening in China."

My Wyness travelled from his Herefordshire home with daughters Sophie, 14, and Ruby, seven, and insisted he had not damaged the figures.

"It is a shame that I have been banned for life because I love the British Museum, all of their exhibitions are wonderful, but the future of my children is more important than my pleasure of visiting the British Museum.

"I know my daughters are proud of me. It was something I had to do to raise awareness of the problem."

Witness Amelia Hanratty, 47, a wedding shop owner of Chippenham, Wiltshire, said: "I saw the man climb over the barriers. He was totally calm and silent. None of the security staff had any idea what was going on.

"They only found out when a member of the public alerted them. Two dashed over and frogmarched him away. He could have damaged the soldiers but he didn't do anything to them except put on the masks."

Mr Wyness was arrested in May for aggravated trespass after chaining himself to a digger in protest at the building of a £12.5 million road in Herefordshire. Then in July he was arrested again after staging a protest at a meeting of Hereford county council during a campaign to save the remains of a Bronze Age footpath.

Sources at the British Museum said it was believed no damage had been caused.

A spokeswoman said: "The British Museum can confirm that an incident took place and that the gentleman was immediately detained by British Museum staff. Security measures have been further strengthened." Thousands of people have visited the exhibition since it opened last month.

On display are 120 objects on loan from China, including 12 life-sized warrior figures from an estimated army of 8,000 created to accompany emperor Ying Zheng into the afterlife. Ticket sale records have been smashed, with almost 200,000 pre-sold.