The 37-year-old Kiwi is a born winner and has proved that over more than a decade at the top in both codes of rugby. Whether or not he adds a Heineken Cup or RaboDirect PRO12 winners' medal to his collection over the next two weekends, he will remain one of the most successful rugby players of all time.
His medal cabinet is already full to bursting and currently contains winners' medals from:
• 2011 Rugby World Cup (New Zealand)
• 2003, 2008, 2010 Tri-Nations (New Zealand)
• 2008 Super 14 (Crusaders)
• 2001, 2004 NPC (Canterbury)
• 1999 RL State of Origin (Queensland)
• 1998, 2000, 2006 NRL Grand Final (Brisbane Broncos)
• 1998 RL Test Series v New Zealand (Australia)
• 1997 NRL Grand Final (Brisbane Broncos)
• 1997 RL Test Series v GB (Australia)
There are only two players who have done the north and south double of winning a Super Rugby and Heineken Cup title, Rod Kafer and Doug Howlett, but one player at least will be added to that elite list this weekend. If Thorn doesn't become the oldest Heineken Cup winner, then Ulster Rugby's Pedrie Wannenburg will become the third man to taste success on both sides of the equator.
Thorn already holds the distinction of being the oldest player to play in a Rugby World Cup Final earlier in the season and was only the second man to clinch NRL and Super 14 titles down under, following in the footsteps of Australia's Peter Ryan when the Crusaders won the Super 14 title in 2008.
Thorn joined Leinster from Fukuoka Sanix Blues on a short-term contract in time to play in the Heineken Cup knock-out stages and, after a quarter-final romp against Cardiff Blues, they went to Bordeaux and defeated French giants ASM Clermont Auvergne.
Born on February 3, 1975, Brad will be 37 years, three months and 16 days old on the day of the 17th final. The oldest player to appear in a final so far is Perpignan's replacement hooker Marc dal Maso who was 36 years three months and 10 days old when they lost the 2003 final to Toulouse.
And if Leinster go all the way and lift the Heineken Cup for the third time in four years Thorn will also relegate Leicester Tigers prop Darren Garforth to "second place" in the oldest winners club - Garforth was 36 years, one month and 19 days old when the Tigers won the 2002 final.
So what is the secret of his seemingly endless career at the top?
"I just love my footie. I like being here, the challenge of it and being part of a Heineken Cup," said Thorn.
"Leinster are a great side with a great coaching team in Joe Schmidt, Greg Feek and Jono Gibbes - the whole package.
"Yeah being in the Heineken Cup final is juicy, but basically there's a brick wall between us and the cup in Ulster.
"Wayne Bennett was my Broncos coach and he always said the hardest thing is to get to the final, and what happens then will happen. But the hardest thing is getting there.
"I have been playing and training without a break now for 16 months - which is the most I've ever done in my career - so it's insane but I'd like to be here till the end of whatever we can achieve and hopefully that's deep into this month."
All that after making his debut for Fukuoka Sanix Blues in Niigata within a fortnight of the World Cup Final - "It wasn't pretty but it was a World Cup win, and the World Cup had given us 24 years of frustration," added Thorn.
In the last four years with the All Blacks and the Crusaders, he reckons that rugby took him away from home for 20 months, so he decided after the World Cup Final that wherever rugby took him, his wife Mary Anne and their four children - Brendan (eight), Aidan (seven), David (five) and Neva (two) - would go with him.
That has meant moving from New Zealand to Japan and from Japan to Ireland and now it is life with Leinster and having to adapt to the difference between the two hemispheres both on and off the field.
"In the southern hemisphere at the breakdown area, you have got to get out of there pretty quick. Over here, there's a bit more traffic going on in the rucks.
"In Super rugby they want to play at a quicker tempo while over here it seems like there's a lot more gamesmanship going on in the scrums, so you've got to adapt. It seems like the scrums are a bit more upfront in Super rugby, but there are a lot of technicians up here and they've got all sorts of different things in the playing paddock.
"I look at that Leinster backline. Far out, you know? I look at some of those guys in the Leinster pack, Cian Healy, Sean O'Brien and all these different guys. There's some real talent out there and if Ireland went out as a team and believed in themselves against the All Blacks, you'd think there's a good chance of doing something."