England have called up Wigan hooker Michael McIlorum into the squad for Friday's International Origin match against the Exiles.
The 23-year-old replaces St Helens' James Roby, who suffered a fractured eye socket in his side's Super League win over Leeds last Friday.
McIlorum played for Ireland in the 2008 World Cup under the grandparent rule.
"It was a bit of a surprise but I'm delighted to have this chance," he said.
"I enjoyed playing for Ireland but as a player you want to test yourself against the best players in the world and that's why I opted for the country of my birth.
"I'm a proud Englishman and it will be one of the proudest days of my life if I get the nod on Friday night."
McIlorum joined the England camp at Loughborough University for Monday afternoon's training session ahead of the game at Headingley.
"Michael is just the sort of person you need for a match against the Exiles: he's tough, tenacious and someone who will never take a backward step," said coach Steve McNamara.
"Whilst we're sorry to have lost James, I have no doubts that Michael is a valuable addition to the squad and I'm looking forward to working with him this week."
McNamara has opted not to draft in a replacement for scrum-half Danny Brough, whose hopes of making his England debut on Friday were dashed when he injured ankle ligaments in Huddersfield Giants' victory over Castleford Tigers on Sunday evening.
With Luke Robinson and Richie Myler already in the squad, England are not short of international-standard half-backs.
Robinson was scrum-half in England's last match against Papua New Guinea in November.
McNamara will trim his 21-man squad to 18 on Wednesday morning, when three players will be allowed to return to their clubs to prepare for Sunday's Super League fixtures.
Meanwhile, Exiles coach Brian McClennan has finalised his squad for the game.
Veteran Catalan forward Steve Menzies, Leeds full-back Brent Webb, Warrington hooker Michael Monaghan and St Helens forward Josh Perry are those to miss out.
Monaghan and Perry miss out owing to the rule that only allows three players from one particular club, while Menzies, who would have been the oldest man in the squad at the age of 36, has only just returned from injury. Webb has not been selected, with Warrington's Brett Hodgson set to start at full-back.
"The players have come straight into camp with a great attitude and have gelled really well, which is very positive," said McClennan.
"We are representing all the nations down under and it is an honour to be part of the first ever International Origin game.
"There is a real buzz about the camp and the players are looking forward to training hard this week, understanding our combinations and the way we want them to play."