"Good puzzle would be to cross Dublin without passing a pub" So thought Leopold Bloom in James Joyce's Ulysses. Almost a century later, the puzzle has been solved by Rory McCann - after a number of unsuccessful attempts.
"It was something I'd been aware of and because I'm a computer programmer and heavily involved in Open Street Map (the Wikipedia of maps) I thought I'd have a stab at it," the 30-year-old Dubliner said.
And even though Dublin literary legend Joyce set the puzzle all the way back in 1922 in Ulysses, it took the computer programmer a few attempts to figure it out.
Mr McCann said "It's the kind of thing you can solve with computers, so it took me a few weeks on and off in my spare time, but I had to develop a piece of software first. Once I had the software it only took me 10 minutes to solve."
Rory initially thought he had the Dublin Da Vinci code cracked in 2011 - only to subsequently find there were plenty of pints of Guinness for sale on some streets that he had included.
Three years later, Rory has the most abstemious of routes, crossing the Liffey via the James Joyce Bridge.
The techie has even gone as far as to exclude hotels from his pub-free route through the city to avoid objections.
"On it you have to walk past the corner of the Guinness brewery and people took issue with that, but you don't go near the entrance and even at that it's not like you can walk up and knock on the gate on the quays and ask for a pint," said Rory.