A ban on smoking in English bars, workplaces and public buildings started today in what campaigners hail as the biggest boost to public health since the creation of the National Health Service in 1948.
The chief medical officer Sir Liam Donaldson said there would be teething problems with the change, but he expected people to comply with the new law.
He told BBC TV: "The other places that have introduced it, both overseas and also the other UK countries, have had very few problems. "England is a very big country so there are bound to be some teething problems with implementing it.
"But on the whole, the majority of smokers and non-smokers wanted this change, so I expect people to comply with it very, very straightforwardly." He said he expected a reduction of more than 1 per cent in the number of smokers as a result of the ban.
Deborah Arnott, director of charity Action on Smoking and Health, welcomed the ban. She said: "Smoking is the single most preventable cause of death. "Workers have a right to a safe environment and the harm done by tobacco smoke is now known to be significantly dangerous."
But artist David Hockney, who has been waging a campaign against the ban, called it a "grotesque piece of social engineering" imposed by a "political and media elite".
The English ban means smoking in enclosed public places such as pubs will now be banned across the entire United Kingdom. Wales and Northern Ireland outlawed public smoking in April following the lead of Scotland last year.
Ireland and other European countries have also banned smoking indoors, while some parts of Canada and a number of U.S. states have had strict controls on smoking for years.
The legislation is designed to protect people from the effects of second-hand smoke at work, which doctors estimate kills more than 600 people a year.
A quarter of adults smoke, with the level higher among those doing manual and routine jobs.