"It is going to be my job to pull this programme together and get everyone to realise this. All my former friends from Australia are saying the same thing, so I am excited about the challenge ahead."
Castle, fresh from two World Cup competitions in Europe with the New Zealand team, beat off a world class field, overtaking Sam Webster on the final turn and holding off Australia's former junior world champion Jacob Schmidt and world champion medallist Eddie Dawkins for the victory.
"It's not sunk in. It feels like I have been working towards this for a while so it's pretty exciting," Castle said.
"I got lucky drawing six behind Sam [Webster] because he one of the fastest and strongest so it was fantastic to grab his wheel and hang on to the finish."
Stewart, a multiple junior world champion, and Sexton produced a superb second half of the Madison, controlling the race with a level of nous that belied their years. They won five of the final six sprints to finish with 74 points ahead of the Australian combination of Kelland O'Brien and Rohan Wight on 64.