Some number of years ago I worked for the met dealing with driving offences, including drink drive. We had the old intoximeter in the station, and one lunch we went to the pub (as norm) and after 2 pints of the black stuff (4.1%) came back and did the test. It went straight to green, so therefore I will drink 1-2 pints of equivilant and drive. If the law was zero,then I wouldn't touch a drop. I spoke to a retired chap a few weeks ago who was involved in this drink fly issue with his old company. He said that the 20mg was the limit, but that is the lowest reading the machine can register. Could anyone tell me if that's correct?