Williams appeared ten times in the famous Black and White, scoring 17 tries between his Barbarians debut against Leicester Tigers on 27 December 1973 and his final appearance against Melrose on 4 October 1976. Five of his tries came against Atlantic Provinces in Halifax on the 1976 tour of Canada.

This was at the height of a glittering playing career, in which he made 223 appearances for Llanelli over nine seasons, won 30 caps for Wales including two Grand Slams and four Triple Crowns, and appeared in two tours for the British and Irish Lions. 

Barbarian F.C. President John Spencer, who was amongst Williams’ close friends, said: “It is with great sadness that the Barbarians have heard of the passing of J.J. Williams, a legend in rugby throughout the world, and one of Wales’ favourite sons. 

“A player who was respected by all nations, J.J. had exceptional pace as a Welsh winger and former international sprinter. His prodigious try-scoring on the 1974 and 1977 British and Irish Lions’ tours, together with two Grand Slams and four Triple Crowns with Wales, demonstrates his celebrated natural ability. 

Born in Nantyfflon, near Maesteg, Williams was educated at Maesteg Grammar School and Cardiff College of Education, where he qualified as a teacher. He moved to Llanelli after playing fly-half for Welsh Secondary Schools and wing for Maesteg and Bridgend. 

A talented all-round sportsman, Williams represented Wales at the 1970 Commonwealth Games in Edinburgh before going on to become Welsh sprint champion in 1971 – demonstrating the speed that would be one of his greatest assets as a player.

At Llanelli, he was part of the famous side that beat the All Blacks in October 1972. At the conclusion of the same season, Williams scored three tries in the Welsh Cup Final when Llanelli beat Cardiff.  

In the 1974 Lions tour to South Africa, playing in what is widely regarded as the greatest Lions team of all time, he scored two tries in two Tests against the Springboks – in total, Williams scored 12 tries in 12 matches, including a record-equalling six against South West Districts as the Lions recorded a 97-0 victory.

Tragically, his death comes just days after the passing of his brother Peter, one of Welsh rugby’s most successful club coaches.

Spencer added: “It has been a privilege to know J.J. and he will forever stand as a true Barbarian. Our thoughts and prayers are with his family and friends.”

Williams is survived by his wife Jane and children Kathryn, James and Rhys.