The former Leicester City manager was keen to find out whether the prolific Foxes attacker had any Irish heritage before he made his international debut for the Three Lions.
The Republic of Ireland made enquiries to check if Leicester City striker Jamie Vardy was eligible to play for its national team, according to Steve Guppy.
Vardy has been a key component in Leicester's remarkable Premier League success this season, scoring 22 goals in 34 league games, and former Foxes midfielder Guppy revealed that Martin O'Neill had instructed him to investigate the striker's heritage when he joined Ireland's coaching staff in 2014.