In the end, it all centred upon six questions. Since 2015, Ferrovial, the Madrid-based global infrastructure group, has been tussling with the Irish Revenue Commissioners over a disputed tax liability arising from the partial sale of its investment in the M4 tolled motorway between Kilcock, Co Kildare and Kinnegad, Co Westmeath. It began with a Revenue assessment and then proceeded to a hearing before the Tax Appeals Commission. More recently, the Spanish seller appealed the dispute to the High Court, which has just issued its judgement. In the overall scheme of things for the Irish state, the amount of money…