With Matt Stevens in such form for Sarries but now retired from international rugby I'm wondering how many dual sided international props there have been (ie with both tight head and loose head distinct extended Test careers)? Alex O'Leary, England
The concept of the loose head dates from the early years of the 20th century. At the time there was no restriction on the number of players in a front-row. In Britain the custom was for there to be three fronting an eight-man pack, but New Zealand's game developed with a two-man front-row in a seven-man scrum.
When the All Blacks swept through Europe on their first visit in 1905, the British/Irish sides tried to match their scrum formation. The Welsh, however, hatched a plan to guarantee a scrum advantage for the Test (which they won 3-0).
Although Wales selected a seven-man pack, at scrum time they slipped a forward from the back of the pack to the front so that they always had a man outside either of the two New Zealand hookers. That's how the term "loose head" came into rugby's lexicon.
Since the 1930s the Laws have meant that only three form the front row, but it was not until the late 1960s that props became so specialised that the tight-head and loose-head were expected to fulfil separate functions. Until then, props were expected to pack with equal facility on either side of the scrum.
The player who did much to develop propping into a specialist subject was the Irish expert Ray McLoughlin. He entered the international side in 1962 and became Ireland's captain in 1965, leading them to a Triple Crown challenge against Wales in Cardiff.
McLoughlin was a tight-head during the first half of his long Test career. He thought deeply about the game and after a break from international rugby between 1966 and 1971 he returned as Ireland's loose-head to become a key member of the successful 1971 Lions in New Zealand. He advised coach Carwyn James on scrummaging techniques until an injury in the rough Canterbury match brought his tour to a premature end.
McLoughlin brought his analytical mind to the mechanics of binding, the geometry of feet positions and the directions in which props should apply force in the scrum. More than any other prop of his generation (with the possible exception of his compatriot Syd Millar), he understood the importance of i) the loose-head trying to get beneath his opposing tight-head, and ii) dictating to the scrum-half the timing of the put-in.
He was the first prop to enjoy two substantial separate Test careers in the specialist positions and finally stood down from the international scene in 1975.
Leonard became the world's most-capped prop with 119 Test appearances (including five for the Lions) between 1990 and 2004. He was a loose-head in his first 39 caps for England from 1990 until the 1995 World Cup, when he moved to the starboard side to accommodate Graham Rowntree in the pool match against Italy. Leonard had filled that position for the Lions in two Tests on the 1993 tour to New Zealand and it was as tight-head that he propped in the 1996 and 1997 Five Nations, before returning to the port side when Sir Clive Woodward became England's head coach.
John Griffiths is a widely respected rugby historian and is the author of several sports books, a regular contributor to the Daily Telegraph and co-author of the IRB International Rugby Yearbook. He has provided insight for Scrum.com since 1999.