 Complete the following phrase:  More recently, the Shaughnessy playoff system has been adopted outside of North America. In English rugby union, the format is currently used to determine the winner of the Premiership, and from 201213 through to 201617 was also used in the second-level RFU Championship to determine the team to be promoted to the Premiership. The Premiership and Championship formats differ only in the number of games contestedthe Premiership playoff uses one-off matches, while all matches in the Championship playoff were two-legged. The Premier 15s, launched in autumn 2017 as the new top flight of English womens rugby, uses the same playoff format as the Premiership. The Celtic League in Ireland, Scotland and Wales, now known as Pro14, adopted a system identical to that of the Premiership starting in 