The law has changed since those early days.An officer can demand a breath sample if he suspects that you have been drinking.The police are allowed to stop traffic.As the cases stand there is now nothing to prevent the police stopping every car and, on suspecting then that the driver has been drinking, demand a breath test.Of course, in the 'old days' the police were quite happy to treat anything and everything as either a moving traffic offence or as grounds for thinking that the driver was driving under the influence ! In the very early days you could demand trial by jury and be acquitted because they all felt sympathetic, whatever your technical defence was. Times have changed, that right has gone and the law is much stricter and simpler.