Admitting mistakes can be difficult, correcting them even harder. Labelling cigarette packets with tar yields (plus nicotine and carbon monoxide) was, and is, a mistake. The mistake was not in the conception of the low tar programme, or even in conducting it as a huge experiment with public health. The error was allowing the tobacco industry to control it.

The tar delivery of cigarettes is routinely measured with a machine and, with the exception of the United States, stated on the packet as a legal requirement in almost every country in the world. It is accompanied by measurement of nicotine and often carbon monoxide.

These measurements are now recognised to be misleading for two reasons, as is the simplistic concept of tar as a substance.1 2 ^w1 Firstly, human smoking patterns vary greatly and are not mimicked by the machine. Secondly, modern cigarette design facilitates compensatory smoking (over-inhalation), which may lead to the smoker taking in much greater amounts of …