England centre Joel Tomkins insists making his debut at Twickenham on Saturday justifies his decision to switch codes.
Tomkins swapped Wigan Warriors for Saracens two years ago and while delighted to have made the breakthrough at international level, he admits the Cook Cup contest will be his greatest challenge yet.
"This was always a massive goal for me, probably the biggest goal and the biggest factor in coming over to rugby union," said Tomkins.
"I wanted to play international rugby and I wanted to play at Twickenham, in front of 80,000. Then, ultimately, I want to play in the World Cup. The World Cup is definitely a big goal of mine.
"I've played in a couple of finals for Wigan and played international rugby league. I can draw on those experiences.
"Saturday's going to be one of the biggest, if not the biggest, crowd I've ever played in front of, but I see it as exciting.
"This is the reason I came over to rugby union. I want to play in these games."
While Tomkins is making his debut at Twickenham in front of his parents, his brother Sam will be playing for England against Ireland in the rugby league World Cup.
Sam recently agreed a high-profile move to the New Zealand Warriors and Joel refused to speculate on whether he might play union later in his career.
"Sam's always been a bit special, even as a kid. He's always been the smallest bloke on the pitch, who could do something special," he said.
"Everyone has always known that he had the potential to go on and do special things, which he has done.
"I definitely hope for the next few years everybody can just let him be in New Zealand to do the best he can because he has got a massive challenge ahead of him."
Watch England take on Australia this Saturday. Coverage starts on Sky 3D and Sky Sports 2 from 1.30pm.