John Adam Barclay made his Scotland debut in the 2007 Rugby World Cup match against New Zealand at Murrayfield the day before his 21st birthday.
Even in defeat in that match he produced clear indications as open-side flanker that a long international career lay ahead for him.
His RBS 6 Nations Championship debut followed in the opening match of the 2008 tournament against France at Murrayfield.
Also that year he played in the Cardiff game against Wales as well as the second Test win against Argentina in Buenos Aires and the November internationals against New Zealand, South Africa, and Canada, scoring his first Scotland try in the last of those matches, the 41-0 win at Pittodrie, Aberdeen.
His second came in the opening, frantic 20 minutes of action against Wales in Scotland's second RBS 6 Nations match of 2010 before being named named man of the match for another dynamic all-action display as Scotland defeated Argentina 13-9 in Mar del Plata to clinch a historic 2-0 series victory in the summer of 2010 - the first time Scotland had achieved a series success in 50 years of touring.
In the first EMC Autumn Test that - against New Zealand - he took on the role of acting Scotland captain when skipper Mike Blair was injured, and was named EMC Man of the Match for his contribution to Scotland's home victory against South Africa.
John made a further 20 Test appearances in the two years that followed, starting all but four matches, including a start in all of Scotland's matches in the 2011 RBS 6 Nations, and three RWC 2011 matches in the New Zealand hosted showpiece.
The following year saw John feature heavily once again, as both a mainstay in the 6 Nations, Summer Tour and Autumn Tests, with his part in an historic victory over Australia in a rain- soaked Newcastle, New South Wales a clear highlight.
A year passed before John was again seen in a Scotland jersey, appearaing twice in the Autumn Tests that year before a two-year spell of absence, which ended with a try-scoring replacement appearance in the 2015 Summer Test against Italy, as part of the extended RWC 2015 squad.
Despite missing out on selection for the global showpiece, John was clearly determined to cement his return, with his commitment to club form rewarded with selection in 2016 RBS 6 Nations squad; a chance he took, and was subsequently rewarded, with a start in all five championship games - scoring his fourth international try against Italy, and making a 50th Test appearance in the final game, against Ireland.
John played for Scottish Thistles on the European seven-a-side circuit tournament in Budapest in 2003 and helped Dollar Academy to an impressive 27-14 win against Dundee High School in the Bell Lawrie White Scottish Schools Cup final at Murrayfield in 2004.
Since then he has been awarded several accolades including the Macphail Rugby Scholarship and the Daily Record Sporting Heroes of the Future.
He made a considerable impact playing in the back-row for Scotland under-18 in the 2004 Four Home Unions' tournament and was signed as an apprentice by Glasgow Warriors at the age of 17 that summer 2004.
He played in all five of Scotland’s matches in the 2005 IRB Under 19 World Championship in Durban, South Africa, captaining the team in the opening game against England and scoring the vital try in the win against Romania.
His under-21 international debut was in Falkirk against France in February 2006, and a week later he played against the Welsh at Newport. Because of injury early in that game he missed the Falkirk match against England, but he returned to play in the away wins against Ireland and Italy.
He then played in all five matches in the under-21 world championship in France, scoring a try against Georgia. Later that year he made his Scotland A debut as a replacement against Australia A at McDiarmid Park.
In October that year, less than a month after his 18th birthday, he was included in the extended squad for Scotland’s autumn Tests.
That was even before he had made his Glasgow debut, which followed in November that year, when he made a replacement appearance in the victory against Borders: it was only two days too late for him to claim the record of the youngest player to appear in a Celtic League match.
John had two seasons as an apprentice with Glasgow before he signed a full contract. In the second of those seasons, 2005/06, he played in 17 matches, starting in all six of Warriors’ Heineken Cup pool matches, and in season 2006/07 he played in all 27 of Glasgow’s games, starting in 25.
In February 2007, also that at Perth ground, he again made a substitute appearance when Scotland A beat their Italian counterparts. He then played in all three of Scotland A’s games in the 2007 Churchill Cup in England, making his first start in the 13-9 win against the USA at Henley. That was followed by his selection as one of five uncapped players in Scotland’s squad for World Cup preparation.