The head of road policing in Waikato says he was astounded by a alcohol reading taken from a driver on the weekend.
Members of the public wrestled the keys off a 50-year-old woman seen driving erractically around the Hamilton Gardens carpark about 8pm on Saturday.
Police say an evidential breath test came back at 1919 milligrams of alcohol per litre of breath. The legal limit for an adult is 400 milligrams.
Inspector Leo Tooman says the quick actions of bystanders probably prevented a tragedy.
The woman's licence was suspended for 28 days and she faces the charge of excess breath alcohol, third or subsequent offence.
She will appear in the Hamilton District Court next week.