His third Oscar may only have confirmed what the world already knew – that he's arguably the greatest screen actor of all time – but outside Lansdowne Road on that euphoric Saturday just over 13 years ago, he was just another anonymous face in the crowd.
And it wasn't until a few minutes after he'd departed that my companion revealed that the quiet but affable man standing with his friend in Dublin talking up Ulster's historic Heineken Cup win over Colomiers was Daniel Day-Lewis.
The fact that most of our party didn't recognise one of the most famous movie stars on the planet who was playing the role of just being himself probably pleased this most private of superstars.
But fast forward a few years and the same Daniel Day-Lewis was spotted at another sporting event, this time in Northern Ireland, the North West 200.
Apparently, it wasn't the first time the motorbike fan had been on the north coast, melting into the massive crowds to enjoy the high-octane action without always seeking out the hospitality of the VIP tents.
He even posed for pictures with other racing fans and there are also photographs of him in his leathers and holding his crash helmet at the North West.
Only hours after he collected his Oscar in Hollywood, a Facebook page dedicated to the races passed on congratulations to him from the north coast. And people who know him say he'll have been chuffed by the message.
A number of bikers online have spoken of the actor's willingness to chat with them and give them his autograph.
"He was really lovely, so down to earth," said one woman of the ordinary man who's an extraordinary actor in more ways than one, a perfectionist who goes to astonishing lengths to prepare himself for the parts he's playing.
He will often stay in character before, during and after filming, talking the talk and walking the walk. Or in the case of another Oscar-winning performance in My Left Foot about Christy Brown, the Irish writer and painter who could only control his left foot, he stayed in a wheelchair on set and had to be spoon-fed.
Several of his best-known roles have been of Belfast men including Gerry Conlon, one of the Guildford Four wrongly convicted of an IRA bombing. The late, great Pete Postlethwaite, who played his father in the film, once told me he was in awe of Day-Lewis and his talent and his dedication to his craft.
He spent nights in prison cells and recruited real-life policemen to interrogate him and got film crew members to swear at him and throw water over him. He lost 30lbs in the process.
For the film The Boxer, set in Belfast but shot in Dublin, Day-Lewis trained twice a day, seven days a week for years. Barry McGuigan, who coached him, said he was good enough to turn professional. The late local actor Mark Mulholland, who was in the movie, said he offered to help Day-Lewis with his Belfast accent before realising he didn't need any assistance.
Reports say 55-year-old Day-Lewis adopted the same principles for his meticulous planning for the Abraham Lincoln role in Steven Spielberg's biopic of the American President. He again stayed in character throughout the production and while some cynics have said there's a touch of madness in his method acting, it obviously works for him as his third Oscar will testify.
His second award, by the way, came in 2007 for his role of oil prospector Daniel Plainview in the movie There Will Be Blood.
His friend, the Dublin director Jim Sheridan, who has worked with him extensively, says Day-Lewis is one of the sanest men he knows
Away from the movies, the actor, whose poet laureate father Cecil Day-Lewis came from an Anglo-Irish background, lives in the Wicklow hills south of Dublin with his wife Rebecca, the daughter of celebrated American writer Arthur Miller.
The couple have two sons, Ronan and Cashel, and Day-Lewis is also the father of another boy, Gabriel-Kane, who was born in 1995 after the actor's six-year relationship with French actress Isabelle Adjani.
Day-Lewis became an Irish citizen in 1993 and holds dual British/Irish citizenship.
He is wary of the Press and gets annoyed with journalists who sometimes mock the research he undertakes before filming a movie, not to mention the fervour with which he throws himself into a role.
He has said his work on a character doesn't start on the first day of shooting. He once insisted in an interview: "There is no limit to the amount of time that you take to discover a whole life – it could take six months, a year or a lifetime".
In the same interview, he spoke of his determination as he grew up not to allow his privileged upbringing stand in the way of him living an ordinary life. He said his house was full of great books about art and literature. But he found his release in the home of one of London's most notorious football teams.
"I supported Millwall with great gusto and was on the terraces every Saturday with the rest of the lads," added Day-Lewis, who now plans to retire from the silver screen for five years to spend more time with his family on his farm in Wicklow.