John, the caretaker national coach for the tour to Southern Africa in 1998 and former Pontypridd and Bridgend coach, has guided Llanharan to the top of the Welsh National League Division One this season with six wins out of six.
John will continue with his evening club duties at Llanharan alongside his new temporary regional day job at Rodney Parade.
“Dennis John has joined us on a temporary contract while Clive Griffiths is away with Wales at the World Cup,” said Dragons coach Mike Ruddock. “And, with all of Dennis’ experience, I am sure we will get something positive out of him being with us for the next few weeks.
“Our forwards have been going well so we have been working on trying to get the back line moving the ball wider.”
The first Celtic game this season on a Sunday sees Glasgow Rugby make the trip on a real high after their Celtic Cup quarter-final triumph over Munster.
“Playing on the Sunday has come about through a bit of everything and we are looking for a big crowd,” said Ruddock.
“Glasgow Rugby had a huge victory over Munster in the Celtic Cup quarters last weekend. It was a fabulous result for them and that will have put them in great spirits for their trip to Rodney Parade.
“As we were not involved in the cup ties, we released some of the boys to their clubs last weekend – those who needed to get a game in – while others had a deserved break.
“We have lost both our Celtic League away games so far, against the Scarlets and against Ulster, but we beat the Ospreys at home and the League is all about winning your home games so we will be fired up for this one.”
