Greene King Pub Company has claimed a smoking ban is becoming inevitable - and has launched a non-smoking strategy to prepare pubs for a future handover.
The Rushbrooke Arms at Sicklesmere, near Bury St Edmunds, become the first pub in the group to become smoke-free earlier this month, and three other pubs in Bicester, Windsor and Banbury have now followed suit.
Adam Collett, the pubco's marketing director, said there was capacity for "dozens" more pubs within the Greene King estate to convert to no smoking over the next 12 months.
"Our strategy is to prepare the business for an outright ban, while maintaining the consumer's right to smoke within the law," he said.
"A ban on smoking is now probably inevitable, because of what's happening in Ireland and the will of the government."
Under the strategy, Greene King is ensuring 50% of the bar in food-led pubs is no smoking, and increasing the number of 100% smoke free food areas.
Managers and staff are being given help to give up smoking, including free patches. Cigarette patch vending machines are also being installed in some pubs.
The Rushbrooke Arms was converted after a suggestion by the pub's manageress, Tracey Platt.
Customers have come from as far afield as Ipswich and Cambridge - which more than 30 miles away - to sample the pub's atmosphere.
"Seventy per cent of customers have said they are happy with it," said Platt, a smoker herself. "And we saw about 40 new faces from the village come in over the first weekend as a result."
The pub has become one of the first in the country to receive a National Clean Air Award.