It couldn't have happened at a worse moment: just as Operation Freeflow was getting under way, putting more police on Dublin's streets as a pre-Christmas warning to drink-drivers, an opportunistic thief drove out of the Guinness brewery with 40,000 pints.

About 450 kegs of beer and stout were lifted from under the noses of security guards in what is believed to be the first raid on the historic St James's Gate Brewery at Victoria Quay along the River Liffey.

It took place as the police announced their Christmas traffic blitz, giving warning that 160 officers would be on patrol over the coming weeks and urging motorists in the traffic-choked city to leave their vehicles at home.

The blitz would target drink-driving, speeding, offences involving HGVs, dangerous driving and people not wearing seat-belts, a senior officer said.

Meanwhile, the lone raider, who has already been nicknamed "the Beer Hunter" by Dublin wags, was driving his own HGV through the Guinness security gates, attaching it to a well-provisioned trailer and taking off with the makings of a very merry Christmas.

Arthur Guinness opened the brewery almost 250 years ago with a 9,000-year lease at £45 per annum. By 1886 it was the largest brewery in the world, with an annual production of 1.2 million barrels of extra stout porter.

But tastes have changed and sales of Guinness are in decline, prompting a review of operations by its owner Diageo. Property analysts estimate that the site is worth £2 billion.

The thief's catch of £46,000 might seem like small beer. But that would be to underestimate the iconic regard with which the Irish hold the brewery. It is the Irish equivalent of Michael Fagan's dawn visit upon the Queen in her boudoir or Ian Fleming's Auric Goldfinger knocking off Fort Knox. In all, 360 kegs of Guinness and Budweiser and 90 kegs of Carlsberg were taken from the complex.

Grainne Mackin, a spokes-woman for Diageo Ireland, said: "We've never had such a breach of security prior to this and we're taking it extremely seriously. All CCTV footage on site is being viewed and the Gardai are also looking at CCTV footage along the quays. The haul has a significant value. We have more trailers coming in and out as we are coming up to Christmas. What could they possibly want with all that beer?"

Police have begun an investigation and have appealed for information. They are resisting suggestions that they call it Coldflow, the popular chilled version of draught Guinness.

Thirsty work

- Thieves in Gloucester made off with four lorries full of cans of lager last year, worth £500,000

- Russian tree-planters punctured a vodka pipeline crossing the Latvian border. Customs officials believe that bootleggers had been selling the spirit for decades

- Irish customs officers seized 1,500 litres of pure alcohol from the IRA in 2005 in a raid on the illegal distilleries that helped to fund their operations. Along with the alcohol they found bottling and capping machines and high-quality copies of brand labels, which allowed them to make near-perfect copies of many spirits on an industrial scale