Regan and his World Cup colleagues arrive in Paris on Monday, effectively written off as no-hopers to retain the title they won amid unforgettable scenes almost four years ago.
The Bristol hooker, a battle-hardened survivor of England's successful 2003 campaign, is among a host of thirty-somethings charged with ramming the bookmakers' unflattering odds down their throats.
Regan, Lawrence Dallaglio, Mike Catt, Jason Robinson and Phil Vickery - among others - have seen it and done it all before.
But if England challenge at the World Cup business end in Paris next month, it would unquestionably eclipse all their previous achievements.
Regan said: "I like the underdog position. I have been it most of my life - it is what people thrive on.
"Last time, people expected us to lose against France in the semi-finals. We beat them.
"The day before, nobody expected New Zealand to lose to Australia. They did.
"We are going there as underdogs. No-one expects us to do anything, but that is great. We will use that to ignite us."
Judging by their pre-tournament form, England need a proverbial rocket to have any chance of lighting up a tournament most pundits believe is a three-horse race between New Zealand, South Africa and host nation France.
Home and away defeats against France followed a largely pointless 60-point Twickenham training romp at the expense of Wales' third team, confirming England have still got it all to prove.
Regan though, insisted: "There is a lot more to come from this squad.
"We have things to work on. We know we are not the finished article by a long shot, collectively and individually."
Regan would not have expected to be anywhere near England's 2007 World Cup squad only six months ago.
Having quit Test rugby in frustration at being overlooked by head coach Brian Ashton's predecessor Andy Robinson, he seemed destined to complete his playing days on the Guinness Premiership circuit.
But Ashton had other ideas, and Regan's infectious enthusiasm promises to be an important factor when the World Cup chips are down.
He added: "Down the years, I have learned that if you get an opportunity then you have got to take it with both hands and give it your best shot."