Watson was the stand-out performer for the tourists on the opening day at the Kia Oval with a superb knock of 176 to form the backbone of Australia's score of 307 for four.
The 32-year-old was eventually removed by Stuart Broad, with Kevin Pietersen taking the catch, but Michael Clarke's men still hold the upper hand and will be looking to Steve Smith (66 not out) to keep the runs coming.
And Watson has stressed the importance of building a big first-innings total.
"It was a really good day," he told Sky Sports.
"We knew batting first on this wicket after winning the toss it was going to be really important to try and put up a good day, so it's ended up nicely for us.
"An important part of our success as a team has been to score big in the first innings.
"We know it's going to be more difficult batting in the second innings here, especially as it's going to get a little bit more up and down and turn a bit. So we know how important a first innings total is and hopefully we've got a few more runs in us tomorrow."
Watson can be more than proud of his own performance having notched his first Test century in three years.
And batting at number three, his fourth different position this summer, he feels he is back where he belongs in the line-up.
He said: "I've been up and down (the order) a bit, batted three quite a few times before.
"In the end, wherever the team needs me to bat, I'm happy to do it. I batted at six in the last Test match, but facing the new-ish ball is what I love doing so it's good fun.
"I've been working very hard on my batting. Mentally, I've had to have a deep look at myself a number of times at where my batting's at. Even throughout this tour I've felt like I've been batting well, but just getting out lbw more than anything.
"So I've had to work very hard, source out the right people to give me the information to work exactly what's going to work for me. And it's worked out well in the end."
England paceman James Anderson enjoyed his own personal achievement, with his two wickets today taking him to 326 Test scalps - ahead of Bob Willis and behind only Sir Ian Botham on the country's all-time list.
And although the Lancashire player acknowledged it was Australia's day, he insists it is not all doom and gloom for the hosts.
He said: "We had some good patches of pressure. We could have got Watson earlier but for the drop, there were a few lbws which could have gone our way on a different day but we stuck at it as best we could.
"We would have liked another one with the new ball tonight if we're being greedy, but we can come back tomorrow with a reasonably new ball and try and make inroads in the morning."