In addition, the winners of the each Shield would be determined by the games played amongst the teams within their regional group, reaffirming its status as a specifically national championship.

[9][10] In Scotland, the 'national' trophy is considered to be the 1872 Cup played exclusively between the two Scottish clubs, usually as a double header over the Christmas and New Year periods.

Derby games have become a tradition in all five member nations over this holiday period, with most home teams achieving bumper crowds for the matches.

Two South African teams - Southern Kings and Cheetahs joined the competition in 2017 to create Pro14, while the four remaining professional franchises stayed in Super Rugby.

The competition adopted a modified two-conference format rather than a full round-robin single table, with extra fixtures to maintain national derby matches.

Also starting in the 2014–15 season, Italy's Nuvolari began broadcasting the games involving the two Italian clubs live on its digital free-to-view channel.

On 30 April 2018, PRO14 Rugby signed a partnership with Premier Sports and FreeSports to broadcast every Pro14 game live in high definition across the UK for at least the next three years.

FIR had two possibilities – either entering four existing Italian clubs from the National Championship of Excellence into the league; or creating two teams of Italy-qualified players exclusively for the competition.

[36] On 18 July 2009, the FIR announced that Aironi and Praetorians Roma would compete in the Celtic League from the start of the 2010–11 season – beating bids from Benetton Treviso and Duchi Nord-Ovest.

[42] By 8 March 2010, a deal had been finalised for Aironi and Benetton Treviso to enter the Celtic League from the 2010–11 season, with each team guaranteed a place in the Heineken Cup.

[43] At the end of the 2011–12 season, however, Aironi were no longer available to compete in future competitions as a regional club, as, on 6 April 2012, they were refused a licence to continue on financial grounds.

In a 2016 interview with The Irish Times, IRFU CEO Philip Browne indicated that the Pro12 was seriously considering establishing a US franchise on the country's Atlantic coast in the near future, seeing the recent growth of the sport in the US as an opportunity to help close some of the financial gap between Pro12 and Europe's two major domestic leagues, the English Premiership and France's Top 14.

[54] In August 2016, Pro12 officials began talks with the unions of both Canada and the United States about expansion before the end of the decade, with interest in putting teams on the east coasts of both countries.

[55] In September 2016, it emerged that Vancouver and Houston may be target cities, primarily due to weather considerations, though the distance from the other teams may make that more of a challenge.

[56] While the North American plan remains active, media attention turned in 2017 toward a new possibility of South African teams entering the competition.

Pan-Celtic tournaments were proposed throughout the early professional era, with the creation of the Heineken Cup in 1995 demonstrating that inter-domestic competitions were financially viable.

The Welsh Rugby Union voted to create five new regional sides (Cardiff Blues, Celtic Warriors, Llanelli Scarlets, Neath–Swansea Ospreys and Newport Gwent Dragons).

Reformatted into a traditional league competition (double round-robin style, all clubs play each other twice, once home, once away), which meant that a season long 22-round match program was launched, and with a new strength in depth due to the amalgamation of Welsh teams and the continuing strengthening of Irish and Scottish teams through the re-signing and retention of star players, the league has been in rugby terms a success.

Scarlets had a disappointing campaign as typical Welsh underdogs the Dragons had a great season, eventually finishing mid table and comfortably qualifying for the Heineken Cup.

Ospreys easily overcame Munster at home in the first semi-final in Swansea[82] while Leinster beat the Glasgow Warriors in the RDS after giving up a strong lead.

All four teams showed they were worthy contenders in the next round with Leinster needing to score a late try to beat Ulster 13–9 in Dublin while Glasgow just got past Munster in Scotstoun by one point to win 16–15.

Leinster were the defending champions having beaten Glasgow Warriors in the previous season's playoff final, to become the first team in the league to successfully retain the trophy.

Glasgow Warriors finished the regular season on top of the table, and were crowned champions for the first time, beating second seeded team Munster 31–13 in the final.

[91][92][93] Thus, the Warriors became the first Scottish team to win a professional trophy, beating Edinburgh's appearance in the final of the 2014–15 European Rugby Challenge Cup.

Despite not ultimately finishing top of the league, they converted their form into a maiden championship title in the post-league play-off matches, including a home semi-final victory over reigning champions Glasgow Warriors, and the Pro12 Final against league-topping Leinster at the neutral venue of Murrayfield Stadium in Edinburgh.

Leinster would regain the title at the Aviva Stadium in Dublin and would become the first Pro14 side to ever win a European and Domestic double, they did so by beating previous holders Scarlets in a high scoring affair, 40-32.

The fourth ranked eligible team in each conference met in a play-off match with the winner taking the seventh Champions Cup place.

That year's competition also featured the first grand final not to contain a single Irish team as the losing finalists, the Bulls, were also South African.

The inaugural winners of the Irish, Welsh, South African and Scottish-Italian URC Shields were Leinster, Ospreys, Stormers and Edinburgh respectively.

The Pro14 Rainbow Cup was a one-off 'transitional' or 'Spring Season' tournament created to facilitate the integration of the four South African sides into the United Rugby Championship.