A nd then there were two. In the season and title race that keeps on giving, a story for the ages is developing. No, no, it’s not that one, as historic it would be for Hearts to break the dominance of the Old Firm and win the league for the first time since 1960 . That’s because Martin O’Neill returning to Celtic , at the age of 74, and winning a fourth title, 21 years after his last in Scotland, would be a pretty decent tale in itself. Consider where he was a few months ago. When Celtic came calling and O’Neill’s phone rang in late October, the Northern Irishman was sat in the TalkSport studio singing the praises of Hearts , the league leaders, after their excellent start to the season. At that point it was largely assumed O’Neill was retired. The previous month saw the release of his book, The Changing Game , where he appeared rather unimpressed by some of football’s emerging trends - sporting directors and data analytics among them.…