LONDON (Reuters Life!) - Bosses of London's O2 arena were cautioned but escaped a fine on Wednesday after two members of the Rolling Stones defied England's new anti-smoking law and lit up on stage.

Keith Richards and Ronnie Wood were pictured smoking on stage during their concert at the new arena on Tuesday night.

Newspapers reported that stewards scrambled to stop onlookers from following suit, even threatening to evict those who lit up.

The law, which came into force on July 1, prohibits smoking in public indoor places. Landlords can be fined 2,500 pounds.

More than 20,000 fans watched the ageing rockers kick off the UK leg of their latest tour, A Bigger Bang at the former Dome in Greenwich, southeast London.

In a statement, a Greenwich Council spokesman said: "We have reminded the O2 of their obligation to enforce smoking legislation.

"We are satisfied with the assurances they have provided that this will not recur."

A spokeswoman for the arena said: "A band member appeared to have a cigarette. However it was extinguished almost faster than the message to put it out got to stage.

"We are sure it was an oversight and are grateful for their co-operation. Along with the rest of the country, we take the smoking ban seriously."

But a source close to the band told The Times: "Ronnie and Keith have been smoking on stage for the last three decades and they're not going to stop for the next two.

"Of course they're going to have a fag -- it's what they do.

"You might say that Keith and Ronnie lighting up while they swap licks is part of the Stones performance."