The 24-year-old middle-order batsman had shown some encouraging signs in the first four Ashes Tests especially with his 89 at Old Trafford, but that elusive first century still hadn’t come his way.
He remained 66 not out after Day 1 of the Fifth and final Test at The Oval having been there when Shane Watson brought up the third ton his career on Thursday.
Smith was beginning to feel nervous has he entered the 90s during the middle session of Day 2 after the opening to play was delayed by rain until after lunch, but once he saw the part-timer Trott come on to bowl he instantly felt more confident of reaching triple figures.
The experienced Brad Haddin gave him the green light to try to hit Trott for six to try to bring up his century and that's exactly what Smith did with a glorious lofted on-drive that had no trouble heading into the stands.
That brought up his first century in his 12th Test match for Australia as he became the youngest Ashes centurion for his country since Ricky Ponting's ton as a 22-year-old at Leeds in 1997.
While Haddin might not have agreed that Trott's bowling provided easy runs when he got out to him soon after, Smith was delighted he got the chance to bring up his century against him rather than being made to work harder by James Anderson or Stuart Broad.
"I probably wouldn’t have played quite the same shot if it was someone else bowling," Smith said.
"Jonathan Trott is obviously a part-timer and doesn’t bowl too often and I asked Hads between overs about what he thought about me just hitting him over his head, and he told me to just keep a clear mind and to go for it if it was there.
"It was there and I managed to get it away. It was an unbelievable feeling. Obviously I'm playing my 12th Test now and I would have hoped it would come sooner, but it's a great feeling to get 100 in a Test match."
Smith did feel like he had been batting well throughout the Ashes series to date but had just been finding ways to get out after getting set.
He had a golden chance that he blew at Old Trafford, but felt he would get another chance if he continued to hit the ball the way he was and it's a good reward for the work he has put into his batting over the past 12 to 18 months.
"I didn’t think it was far away. Obviously it was disappointing to get out on 89 at Old Trafford to a pretty silly shot, but I feel like I've been hitting the ball really well and that my patience has been pretty good. I hoped it wasn’t too far off and today was the day," he said.
"I have worked on a few different things. I've been trying to get over my front knee a little bit more and I've got a little bit of a bat tap that I used to have which made me push at the ball so I think I have limited that a little bit. I still have work to do as everyone does, but I feel like I am in a good place and improving."
While Usman Khawaja, Phil Hughes and Ed Cowan have all been dropped during the Ashes series for failing to deliver big scores, Smith wasn’t feeling any extra pressure to reach triple-figures at The Oval but was delighted to do so and to see Watson score a brilliant opening day 176 as well.
"I probably was under a bit of pressure but I was trying to put that in the back of my mind and just go out and play the way I always play," he said.
"I didn’t think too much about it and just tried to go out and get runs, and it was nice to form a partnership with Watto yesterday. He batted superbly and we were able to put us in a strong position in this Test match."
While Australia is three-nil down in the series, Old Trafford was heading their way before the Manchester rain intervened and there has been time elsewhere in the series where they have been in strong positions.
There have been batting collapses that have let Australia down, but overall there have been enough good signs to give them confidence for the return series this summer in Australia and that's how Smith is looking at things.
"I think we have to just take the positives out of this series," Smith said.
"The sessions that we have lost have seen us lose big clumps of wickets, but looking forward it's always a positive knowing that we are playing good cricket and we do have that in us.
"We know the brand of cricket we are looking to play going forward and we want to finish this Test match strongly, and hopefully it's all positive heading back to Australia and we can carry on with this form."