Until June 2020, he was a member of the Elite Panel of ICC Umpires and officiated in international matches - Tests, ODIs and T20Is.

Llong made his first-class cricket debut for Kent in 1990 and won his county cap in 1993.

He also played club cricket at Green Point CC in Cape Town during the early 1990s.Nigel Also played for Ashburton Cricket Club in Australia for 3 seasons in the 1990s as Captain Coach Llong officiated in his maiden first-class match in June 2000.

As with all members of the ICC International umpire panel, Llong is eligible to serve as the home umpire in ODIs in England, and can also be appointed by the ICC to stand in ODIs and Test matches away from England as a neutral official.

Llong was selected to be a reserve umpire for the 2007 Cricket World Cup, but was not called upon to officiate at any point in the tournament.