The Wales No 10 lined up with his Scarlets teammate Gareth Davies for the opening game in the Vodafone Summer Series and grew into the game as he laid down his marker for possible World Cup selection.
On the other side of the fence, the Leicester Tigers scrum half Van Portvliet came on in the second half and couldn’t do anything to stop his side from slipping to a 20-9 defeat. He and Costelow used to go to school together when they were in the Tigers Academy.
“I went to Oakham School with Jack, and it was nice to see him afterwards. There were no messages between us in the week, I just kept my head down,” said Costelow.
“On the whole, I thought it was pretty good and the boys put in a lot of effort. It was a brilliant occasion, really special, and it was great to see a near enough full crowd
“I’ll take a lot of learnings from the game – it showed me where I want to be and where I can get to. There is a lot of room for improvement but on the whole, I thought it was good.
“I’ve been doing a lot of work with Neil Jenkins in training, and he has been helping me with kicking and the game-management side of things. It is about keeping on improving.”
It was Costelow’s inch-perfect cross-kick to Aaron Wainwright that paved the way for the opening try. That really was a major turning point in the game.
Costelow is battling it out with Dan Biggar, Gareth Anscombe and Owen Williams for a place in Wales’ final World Cup squad.
“You just have to work hard every day, and when you get the opportunity to try and perform. That is the biggest mindset, really, turning up every day and trying to improve,” added Costelow.
“We probably struggled to get out of our half in the first half, but in the second half we managed to find a way and we started putting some phases together. I thought we had some decent outcomes.
“We played in the right areas and got opportunities higher up the field. We started creating chances, which we probably didn’t do in the first half.
“Finding a way to win was massive.”