Roy Keane follows in a lengthy line of Republic of Ireland players to have represented Celtic, including the latest, 19-year-old Aiden McGeady who, this week, was named the Scottish Premier League's young player of the month for November.

Several of Keane's former Irish team-mates played at Parkhead, most notably Packie Bonner who spent over a decade with the club. Tony Cascarino had a considerably less successful spell in Glasgow after he was signed by Liam Brady from Aston Villa in 1991, scoring just four goals in six months. Granted, one of them was an equaliser at Ibrox, a goal that very nearly rescued his standing with the fans.

Irish full-back Chris Morris and forward Tommy Coyne also played both for Celtic and alongside Keane for Ireland, as did, ironically, Liam Miller. Miller, now on loan at Leeds United, was billed as the 'new Roy Keane' when he was signed by Manchester United; Keane will now fill one of the midfield roles Miller vacated when he left Parkhead.

There was, of course, another Irish team-mate of Keane's who played for Celtic, between 1987 and 1989. We could be wrong but we're guessing that phone calls will not be exchanged in the coming days, with the Celtic old boy offering the newcomer some helpful advice. And who might he be? Yep, Mick McCarthy.