The Celtic Warriors scrum-half spotted the opening down the blind-side from the base of a scrum and dived over untouched.

But a fumble from full-back Rhys Williams allowed Tongan fly-half Pierre Hola to pull the score back almost immediately.

The boot of fly-half Stephen Jones, with nine points from three penalties, was the difference in a rugged, error-strewn encounter.

Rhys Williams then sent Mark Jones away down the left, and although he was halted just short of the line – with even the slippery conditions not helping him slide over – Wales earned a five-metre scrum from a Tongan knock-on.

The Welsh opted for a number eight pick up from Alix Popham, but the Tongan defence remained solid, forced the knock-on and cleared.

But the kick from Va’enuku reached only the 22 and Wales, dominant in the lineout, retained possession and slowly tightened the screw.

Scrum-half Gareth Cooper, who will be a team-mate of opposite number Silicon Martens at the Celtic Warriors after the World Cup, scampered over untouched from the base of a Welsh scrum.

Set just five metres in, Tonga had ignored the blindside and Cooper pounced to dive over and extend Wales’ lead to 11-3, with Jones missing the conversion.

Cooper then almost came unstuck as Tonga pounced on a loose ball that the 24-year-old had fumbled.

Tu’ifua beat Jones on the outside, but his chip forward slid into touch just metres from the line.

But handling was increasingly tricky and Williams was soon caught out as he failed to deal with a stab through from Hola and the newly-installed fly-half followed in to touch down under the posts.

Hola, who successfully completed 17 conversions in Tonga’s 119-0 World Cup qualifier victory over Korea, then converted but sent a 38-metre penalty just wide as Wales retained the lead.

Mark Jones almost extended it with a try four minutes before the interval, only to be brought back for a forward pass, but Wales had the penalty for Tongan offside and Stephen Jones slotted it over.