Professor Susan Jebb told The Times that people tend to “undervalue the impact of the environment” in making choices.

“If nobody brought cakes into the office, I would not eat cakes in the day, but because people do bring cakes in, I eat them,” she said.

“Now, OK, I have made a choice, but people were making a choice to go into a smoky pub.”

She said the public had recognised that anti-smoking efforts can be made “more successful by having a supportive environment”, but we “still don’t feel like that about food”.