There was a time when the job of picking a national side was a clear-cut procedure - with the fundamental requirement being that the player was from that country.
However as the years have passed, the lines have blurred somewhat to the point where players are able to switch allegiances by serving either a three-year residency period, or having a relative born in that country.
That has meant national coaches - and the union bosses - can effectively look at bringing in overseas players with a view to them representing their new home in the future. The phase of the day being "project players" to describe the tactic.
The players, themselves, can also look to achieve their international ambitions by pinning their colours to another mast.
Following the decision of Ireland, England and Wales to bolster their squads with foreign-born players - Richardt Strauss (South Africa), Mako Vunipola (New Zealand, with his father having captained Tonga) and Aaron Jarvis (England) - we look back at a 'flag of convenience XV' from the home unions.
15 Shane Howarth (Wales)
The former All Blacks international was at the heart of the 'Grannygate' scandal that rocked rugby and forced a change in the IRB eligibility rules. Howarth was capped four times by New Zealand before switching his allegiances to Wales in 1998 after joining Newport. Howarth claimed his grandmother was from Wales - therefore clearing him to play - however an investigation later proved she was born in New Zealand. Howarth's international career was brought to a shuddering halt, while the IRB subsequently blocked players from representing more than one country.
14 Tim Visser (Scotland)
The talented Edinburgh winger is currently being used as why 'project players' can be good for the game and individuals. Had the three-year residency ruling not been in place, then it is unlikely that the try-scoring talents of Visser would be seen on the world stage. Born in Holland - and the son of a former Dutch captain - Visser would have been limited to playing in the lower echelons of the international game. However Scotland's gain really is Holland's loss - particularly given the investment currently going into the game in the Netherlands.
13 Sean Lineen (Scotland)
The original 'Kilted Kiwi', Lineen was born in New Zealand - with his father Terry having won 12 caps for the All Blacks. However he initially played for Pontypool after arriving in the UK before moving to Boroughmuir. With his Scottish ancestry - via his grandfather - Lineen went on to play 29 times for his adopted home, including in the famous 1990 Grand Slam-winning side. Fellow New Zealand-born Scots Brendan Laney (20 caps) and John Leslie (23 caps) could also have claimed the centre berth in our side.
12 Shontayne Hape (England)
It is unlikely Hape's stint in the England side will be remembered with great fondness by fans, with the cross-code convert dividing opinion. Born in Auckland, Hape made his name in the 13-a-side code and represented New Zealand before he switched to union in 2008. His Test debut for England came soon after he served his residency period but Hape struggled to make an impression and he won just 13 caps before he opted to head to the Top 14 in France. Hape is not the only overseas centre tried by England - with compatriot Riki Flutey, South Africa-born Stuart Abbott and current star Manu Tuilagi (whose brothers Henry, Andy, Alesana and Freddie all played for Samoa).
11 Lesley Vainikolo (England)
Big things were expected from 'Big Les' following his much anticipated switch from rugby league - where he had played for Canberra and New Zealand before a free-scoring spell at Bradford. However the 'Volcano' failed to erupt for England - with Vainikolo struggling to cope after he was fast-tracked into the national set-up. He made just five appearances in 2008 before he was discarded, never to be seen in the England senior squad again.
10 Mike Catt (England)
There is little doubting Catt's loyalty to the England cause, with the versatile back making 75 appearances during a controversial career. Now part of the England backroom staff, Catt went on win the World Cup in 2003 before inspiring an unlikely run to the final four years later. Catt would also play for the British and Irish Lions - not a bad record considering he was born and bred in South Africa and only arrived in England as a 21-year-old.
9 Isaac Boss (Ireland)
The scrum-half was been born in Tokoroa and his livewire talents saw him represent New Zealand at Under-19s level. He also played for the Hurricanes and Chiefs before he headed to Ulster (and subsequently Leinster). His Ireland ancestry cleared him to switch countries - and he ironically made his debut against the All Blacks in 2006.
1 Dave Hilton (Scotland)
Bristol-born Hilton had made 41 appearances for Scotland between 1995-2000 under the belief his grandfather was from Edinburgh. However as part of the 'Grannygate' revelations that rocked the sport, investigations revealed his grandparent was in fact English - curtailing the prop's international ambitions. Hilton, though, returned to the Scotland side through the residency ruling after moving north to play for Glasgow. He made just one more appearance - off the bench - before disappearing back into the international wilderness.
2 Dylan Hartley (England)
Hartley finds himself in the mix having been born and raised in New Zealand. England, though, will claim that they have played a crucial role in his development into one of the world's leading hookers. Having first arrived in the country to stay with relatives, Hartley was recruited to the age-grade set up. Hartley's mum is also English - but that has not stopped him facing criticism for his switch of allegiances.
3 Chris Horsman (Wales)
The prop was at the centre of a tug of war for his services during his playing career, before Horsman finally opted for Wales. Having been born in Buckinghamshire and played for England at age-group levels, he seemed certain to play for the senior squad. However a move to Bridgend saw him approached by then Wales coach Steve Hansen about a possible switch. And having completed his three-year residency - he continued to live in the country despite playing for Worcester - Horsman went on to win 14 caps for Wales.
4 Brent Cockbain (Wales)
The Australian-born lock qualified to play for Wales via the residency ruling, having moved to Pontypridd via London Irish. Cockbain, though, had previously played for Australia Under-19s and Under-21s, while his brother Matt was the heartbeat of the Wallabies pack. Hailing from New South Wales, Cockbain played for the Reds before moving to the UK. After a season at Exiles, he headed to Wales and went on represent Pontypridd, the Celtic Warriors and the Ospreys - winning 24 caps along the way.
5 Nathan Hines (Scotland)
Another Australian-born lock, Hines was able to switch allegiances to Scotland via his grandmother. Born and raised in Wagga Wagga, New South Wales, Hines went on to play rugby league in his youth before taking up union. He made the move to Scotland in 1998 - playing first for Gala before joining Edinburgh. His international debut followed in 2000, with Hines going on to make 76 appearances, while he toured with the British and Irish Lions in 2009.
6 Martin Leslie (Scotland)
Leslie joined his brother John in claiming a place in the Scotland side via their grandfather. Having been born in New Zealand, the Leslies came from a strong rugby background - with their father Andy having captained All Blacks in the mid-1970s. Martin, who moved to Edinburgh from the Hurricanes, went on to make 37 appearances for Scotland, scoring 10 tries.
7 Brett Sinkinson (Wales)
Sinkinson, along with Howarth, believed he was eligible to play for Wales courtesy of a grandparent. However his career was put on hold after the New Zealander discovered his grandfather was from England and not Wales. Sinkinson, who had joined Neath from the Bay of Plenty, recovered from the 'Grannygate' scandal to play for Wales once again under the residency ruling - winning 20 caps in total.
8 Dion O'Cuinneagain (Ireland)
The No 8 has the honour of having captained two countries -leading the South Africa Sevens team before going on to skipper Ireland. O'Cuinneagain was born in Cape Town, with his form for Western Province earning him a place in the sevens set-up. However he opted to leave his home for the UK, first playing for Sale before moving to Ballymena and then Ulster. His international debut followed on the tour to South Africa, while he was handed the captaincy in 1999.
The next to turn...?
Michael Paterson (Wales), Andre Pretorius (Wales), Ernst Joubert (England), CJ Sander (Ireland), Quinn Rouz (Ireland), Danie Poolman (Ireland), Hanno Dirksen (Wales), George Earle (Wales), WP Nel (Scotland), Joshua Strauss (Scotland), Billy Vunipola (England)