London - Ireland great Brian O'Driscoll is set to equal George Gregan's world record for the most Test appearances when he runs out against England in the Six Nations at Twickenham on Saturday.
The midfield maestro in his final season before retirement, has overcome a stomach bug and is now on course to tie former Australia scrum-half Gregan's world record of 139 caps.
All of Gregan's Test career was spent representing the Wallabies, whereas the record of O'Driscoll, on the brink of playing his 131st Test for Ireland, also includes eight appearances for the combined British and Irish Lions.
Fitness permitting, the 35-year-old O'Driscoll should break Gregan's mark before the end of the Six Nations, with Ireland concluding the tournament against Italy and France following this weekend's visit to London.
"Brian trained fully on Thursday, and in fact he could have trained on Tuesday, but he just was still feeling the after effects of an illness," said Ireland coach Joe Schmidt in a news conference broadcast on IrishRugbyTV after he announced an unchanged starting side Thursday.
"And with his experience and know-how he's in a good position to know what he needs, and he brought that to bear," the New Zealander added. "He's fully ready to go now though."
Schmidt stuck with the same 1st XV as the Six Nations leaders look to continue their quest to see centre star O'Driscoll off with a Grand Slam following Dublin drubbings of Scotland (28-6) and defending champions Wales (26-3).
However, he did change his bench with Iain Henderson in for the injured Dan Tuohy and Jordi Murphy providing back-row cover in a match where Ireland will try to end a run of three straight defeats by England.
"There have been some challenges that would stand out in my mind but none as tough as this," said Schmidt.
And Ireland captain Paul O'Connell said the team were braced for an increase in intensity following their one-sided wins over Scotland and Wales.
"The lads realise what a step up this is and there's a realistic view of where we need to be to win this match," he said.
"The confidence isn't sky-high, it's realistic," the Lions lock added.
"The last three times we've played England we've lost to them.
"The way we've been playing in recent times, particularly our last three games, we've been good.
"But in physicality, fitness and mental stakes the step up is huge.
"England have spoken a lot about making Twickenham a fortress, but we know that's exactly what it is."
Ireland team announced Thursday to play England in a Six Nations international at Twickenham on Saturday:
15 Mike Brown, 14 Jack Nowell, 13 Luther Burrell, 12 Billy Twelvetrees, 11 Jonny May, 10 Owen Farrell, 9 Danny Care, 8 Billy Vunipola, 7 Chris Robshaw (captain), 6 Tom Wood, 5 Courtney Lawes, 4 Joe Launchbury, 3 David Wilson, 2 Dylan Hartley, 1 Joe Marler
Substitutes: 16 Tom Youngs, 17 Mako Vunipola, 18 Henry Thomas, 19 Dave Attwood, 20 Ben Morgan, 21 Lee Dickson, 22 George Ford, 23 Alex Goode
15 Rob Kearney, 14 Andrew Trimble, 13 Brian O'Driscoll, 12 Gordon D'Arcy, 11 David Kearney, 10 Jonathan Sexton, 9 Conor Murray, 8 Jamie Heaslip, 7 Chris Henry, 6 Peter O'Mahony, 5 Paul O'Connell (captain), 4 Devin Toner, 3 Mike Ross, 2 Rory Best, 1 Cian Healy
Substitutes: Sean Cronin, Jack McGrath, Martin Moore, Iain Henderson, Jordi Murphy, Isaac Boss, Paddy Jackson, Fergus McFadden