In his time at Ponty, Johnston was selected for Wales U21s and Wales 7s and was involved in the squad that won the Welsh Cup in 2002 and narrowly lost to Sale in the Parker Pen European Shield Final. After regional rugby was formed he returned to Neath RFC winning the league twice and Welsh Cup in a three-year stint.
At Ponty, Johnston was selected for Wales U21s and Wales 7s and played with the squad that won the Welsh Cup in 2002 and lost narrowly to Sale in the Parker Pen European Shield Final. After regional rugby began, he rejoined Neath RFC where he won the league twice and the Welsh Cup over a three-year span.