The campaigners believe history, science, demographics and changing attitudes are all on their side. ''There are no public health people that I've met, whether academics or workers working with young people in alcohol and drugs, that think this is a bad idea,'' Carr-Gregg said. Those who would be affected by raising the drinking age have mixed views on the concept. ''I think it would be very difficult to enforce and I am not sure how effective it would be, but I think by itself it is probably a good idea,'' said Courtney Darville, 18, a science student who was among the youthful patrons seeking respite from the heat on Thursday with a few quiet ales on the Manning Bar balcony at Sydney University. ''A nanny state doesn't work,'' said fellow student Oliver Lotz, 20, who confessed he first got drunk at 13, and began to drink fairly regularly from 16. ''The reason that I got drunk, and I think other people would, is because you are at a certain stage in life in terms of your physical maturity, your school life, your social interactions and your access to alcohol. That doesn't change just because the legal age has gone up,'' he said.

Moral panic about young people and alcohol is not new. But neuroscience from the past decade now suggests the brain keeps developing up to age of 25 and is adversely affected by excessive alcohol consumption. It may be what ultimately clinches the debate in favour of raising the legal age for buying liquor. ''I don't think people realise there is a massive change occurring at the moment amongst the secondary school population,'' Professor John Toumbourou, chairman in health psychology at Deakin University, said. He co-wrote a research paper for the campaign with Dalgarno Institute executive director Shane Varcoe. A 2011 survey for the Australian government's drug strategy found the proportion of 12- to 15-year-olds who consumed alcohol a week before the survey fell from 29 per cent in 2002 to 11 per cent in 2011. ''When we talk to parents and young people, they are saying the reason we are not using alcohol any more is we know it is bad for the developing brain,'' Toumbourou said. ''A huge constituency'' is saying there is ''incredible irrationality'' in laws which effectively require parents to prepare their children for alcohol use just when their brains are at a crucial stage of development. The National Drug Strategy Household Survey appears to bear this out, showing that Australian support for raising the legal drinking age to 21 rose from 40.7 per cent in 2004 to 50.2 per cent in 2010.

Advocates say increasing the legal age would save young lives by reducing car crashes. Studies in the 1970s showed teenage crashes increased when the drinking age was lowered in Australia from 21 to 18 in the late 1960s and early 1970s. US president Ronald Reagan supported 1986 legislation that made federal road funding to US states conditional on them introducing a legal drinking age of 21. A review of 17 studies estimated that under-age crashes fell an average of 16 per cent in the states where this was done. However, despite such evidence, change will be difficult. ''We've had this discussion previously and by and large the general community have rejected it, on the basis that you are saying that at 18 you can go to war, you can vote, you can drive a car but you can't drink alcohol,'' Australian Hotels Association NSW director of policing John Green said. A spokesman for Premier Barry O'Farrell said he had previously ruled out any increase to the drinking age. The fact state laws need to be changed adds complexity: ''The states on the whole have been much more closely aligned with the alcohol industry, regardless of whether they are Coalition or Labor governments, and are very reluctant to do anything to antagonise [it],'' said Wayne Hall, a public health professor at the University of Queensland centre for clinical research.

Varcoe, of the Dalgarno Institute, estimates the campaign might take five to seven years to raise the drinking age. Gordian Fulde, the head of accident and emergency at St Vincent's Hospital in Sydney, knows as much as anyone about the devastation alcohol can wreak on young lives. ''I think in the end it's not going to be socially acceptable [to raise the drinking age] and I don't think it's not going to work,'' he said. ''Just living in Australia will tell you that.'' He doubts ''moving the goal posts'' to 21 will change the core problem - ''our stupid drinking culture about alcohol''. Fulde's ''pet silver bullet'' is to have drunk people photographed or videoed so they can see, when they are sober, how idiotic or obnoxious they are when drunk. It's an idea unlikely to appeal to civil libertarians, though it made Lotz at the Manning Bar raise his eyebrows with interest and amusement. It might just work, he said, and to some extent, it already happens.