An Irish software developer believes he has solved James Joyce's near century-old riddle of how to walk across Dublin without passing a pub.
Rory McCann, 27, claims he has settled decades of debate about the puzzle in Joyce's masterpiece Ulysses with a simple equation proving that it can be done.
Using online maps, the Dubliner worked out an algorithm - a computer equation - which found how to criss-cross the capital, from north to south and east to west, away from the temptation of any pub.
'The puzzle was just one of those things I was aware of, like most people in Dublin,' he said.
'I started thinking about how you would go about it, the pen and paper route which many people have tried, and which gets very tiring very fast, then I decided to try it on the computer.'
The University College Dublin computer science graduate started by plotting out 30 points on either side of the city - 15 along the northside's Royal Canal and 15 along the southside's Grand Canal.
The waterways were traditionally regarded as the city limits around Joyce's time.
Mr McCann, from Shankill but now living in Smithfield, then developed his algorithm to try and find a path between a point on the northside and a point on the southside while avoiding pubs marked on the online map website OpenStreetMap.
This week when he put the riddle-busting route on his blog a number of people got in contact pointing out bars which were not included on the map.
He corrected the route a few times since and is confident now that he has the conundrum conquered.
Mr McCann began trying to crack the teaser last year but when he could not get it finished for Bloomsday, he put it on the backburner until this year's event.
He reckons he has spent weeks working on it over the last 12 months.
Ironically, one of the key sections of his route is along the length of the Guinness St James' Gate brewery, but he points out it doesn't pass the tourist pubs inside.
The computer programmer readily accepts doubts will remain and arguments will continue to rage, as to be expected with the apparent resolution of a brain-twister that has baffled brains since the publication of Ulysses in 1922.
Particularly likely to come under attack from pedantic Joyce fans is his decision to ignore hotels and restaurants which serve drinks and may even have their own bar inside.
'It is a contentious issue,' he admits.
'But they are not pubs. There's also the issue of whether any pubs are missing from the map.
'If anyone finds any pubs that are not there they can add them to the street map and we can see if we can continue to get around Dublin without passing a pub - or maybe there will be a deal-breaker, and we may find it is impossible.
'But I think it is looking good.'
Others have long since claimed the answer to the riddle was simple: You can cross Dublin not passing any pub by simply going into them.
Twitter: Ulysses 140 characters at a time - @11ysses
Capital D will be following the original routes taken in Ulysses from 7pm.