The Storehouse is expected to attract a record 1m visitors this year and there are fears its closure could have a negative effect on Dublin tourism overall.

But relocating the brewery, which produced more than 12m kegs of the black stuff last year, away from Dublin could jeopardise the marketing value of the Storehouse to Diageo. Tourists would be visiting a facsimile of a working brewery rather than the real thing.

A spokeswoman for Diageo told the Sunday Tribune that while the Storehouse is "very much a part of selling the consumer experience of Guinness. . . part of its attraction is that it is part of the brewery".

Failte Ireland considers the brewery important enough to the Storehouse experience that a spokeswoman suggested Diageo would transport tourists to wherever the new location might be.

"I'd imagine they're going to provide some kind of format to take people out [to the brewery], but it's really too early to say, " she said.

Despite its popularity, however, it's a very small drop in the barrel.

The company has 1.7bn in annual Irish turnover, but less than 14m of that comes from Storehouse admissions. Diageo was unable to provide revenue "gures for merchandising.

But the Storehouse's value to the Guinness brand is a little less tangible, as it creates a "brand immersion experience", according to the Diageo spokeswoman. The company considered that experience worthwhile enough to spend 45m on a 2001 revamp of the Storehouse, while the company moved its London brewing to Dublin in a massive expansion just two years ago.

However, much of the St James's Gate site . . . in a prime city centre site . . . has fallen into disuse.

"They might sell off chunks and maintain a core brewery, " said Goodbody analyst Liam Igoe.

"They'd be very conscious of doing damage to the brand, since it could impact sales and valuation."