JP McManus and John Magnier were major shareholders in Man Utd before selling out to the Glazers in 2004. Dermot Desmond is the key player at Celtic but there are few other Irish investors at football clubs across the water.
In 2003, the Sunday Independent revealed that O'Leary had been offered the chance to buy a stake in Manchester City.
"I wrote back a very nice letter saying, 'Thank you very much, I've been a life-long supporter of Man City. They've broken my heart on many occasions -- but I'll confine my support to going to Maine Road twice a year," he told the Sunday Independent.
"Can you imagine buying a controlling interest in an English team? You'd be all over the back pages of the papers."
Sunday Indo Business