A rare bottle of Irish whisky which auctioneers believe could be the oldest in existence is to go under the hammer in London on Wednesday (November 29). The bottle has been owned by one family in Ireland for generations, and this is believed to be the first time in history it has been offered at auction. The label reads 'Glenavon Special Liqueur Whisky Bottled by the Distillers', yet Glenavon ceased operating in 1858. The distillery opened in 1851 meaning the whisky is at least 148 years old - with a maximum possible age of 155 years. "This bottle of whisky is certainly the oldest that we have ever sold in so far as we have ascertained the glass as being mid Victorian and it's come from a distillery that has ceased to operate in 1858. So we can feel confident that its possibly, certainly it's the oldest bottle of whisky that we've ever sold at Bonhams and possibly the oldest that has ever been sold," said Richard Harvey, the head of the Wine Department at Bonhams. Auctioneers expect the half size bottle (approximately 375ml) will fetch between 5,000 and 10,000 pounds at auction (9,580 - 19,160 U.S. dollars) and they believe there will be no shortage of interested buyers. "There are a large number of whisky collectors and whisky collectors are also whisky drinkers so I imagine that and hope that it will be bought by somebody who is a serious whisky collector but will perhaps open the bottle and share it and drink a piece of history," said Harvey. Unlike wine which improves in the bottle but then must be consumed in its prime before it deteriorates, auctioneers are confident the whisky will taste the same as it did the day it was bottled as the lead seal and cork are still in perfect condition. "The whisky should taste perfect. Spirits, once they're bottled do not deteriorate with age and the condition of the bottle, the level are exceedingly good and the whisky should taste pretty much like it did when it was bottled probably 150 years ago." Harvey has his own opinions on how the pricey little bottle should be consumed. "I think with most wines or spirits they're best drunk in company. Obviously whisky you don't need a large tot so that bottle despite being a smaller half bottle could be shared amongst a large number of people and just sipped and appreciated in good company as it was intended." The bottle is an unusual size, it is the same shape as modern day 750ml bottles but it's estimated to be half the size of this. It is made from olive green glass. The liquid inside appears to be pale gold and the level of fluid is high for such an old bottle. The only question that would-be buyers might be asking now that no one can answer is - does whisky made 150 years ago taste better than whiskey made today?