Heather Watson finds peak motivation at the start of the season and she may have scored her best win of 2017 already after dumping Samantha Stosur out of the Australian Open.
Watson made it five British players into round two in Melbourne for the first time since 1987 after Kyle Edmund and Johanna Konta also progressed.
Naomi Broady nearly made it six but was edged out by Australian 22nd seed Daria Gavrilova, calling the crowd "pretty harsh" with their bias towards the home player. Andy Murray and Dan Evans had already won on Monday.
Stosur, seeded 20th in Melbourne and a local favourite despite having a dismal record at her home tournament, is the highest-ranked opponent, at 21st, that Watson has ever beaten at a Grand Slam.
In 17 attempts against players in the top 50, this was only her second success, the other coming in a mammoth match against Frenchwoman Caroline Garcia at Wimbledon in 2015.
Watson's 6-3 3-6 6-0 victory also marks a dramatic upturn in form, given she failed to go past the second round of any tournament from June last year and watched her ranking drop from 50th to 81st.
Asked for the cause of the difference, Watson said: "Because I'm fresh. I haven't played in a while so I'm motivated. I've had that time off and been at home.
"When it gets hard for me is when I've done too many weeks on the road and all I think about is going home.
"You have those weeks sometimes and you have to tough through them but it's not good when it becomes every week. I want to manage that better.
"I need to listen to my body. I think (the Olympics in) Rio was a big part of it last year. I talked about it a lot, was really looking forward to it, wanted to make it.
"Then I made it and once it was done I was like, 'I just want to go home'. I was dead."
Broady provided more evidence of her excellent progress in the day's final match on Margaret Court Arena but lost out to the Russian-born Australian Gavrilova 3-6 6-4 7-5.
"It helped 'Dasha' a lot having the crowd behind her - when it's such a close match that makes a big difference," Broady said.
"They were pretty harsh the longer the match went on. They started shouting between first and second serves but I've had worse so I was prepared for it."
Serena Williams delivered an emphatic message about her form and fitness as the American breezed through a fiendish first round against Belinda Bencic.
Williams has only played two competitive matches since the US Open in September and many predicted a tough test against Bencic, under-ranked due to injuries at 59 in the world.
The No.2 seed, however, showed few signs of rust on Rod Laver Arena, dispatching Switzerland's Bencic 6-4 6-3 to advance to round two.
Williams will now face the Czech Lucie Safarova in a repeat of 2015's French Open final, which the 22-time Grand Slam champion narrowly won.
After losing in the US Open last four in September, Williams skipped the rest of last year in a bid to overcome a niggling shoulder problem.
Her return in Auckland earlier this month did little to inspire confidence as she was beaten by fellow American Madison Brengle, ranked 72nd in the world.
Bencic has more pedigree, as well as a victory over Williams in 2015, but she ran into the 35-year-old in defiant mood.
Williams hit eight aces - often a strong indicator of her form - and 30 winners, and despite a minor slip-up in the second set, never looked in danger.
"She was just recently in the top 10 so I knew it would be one of the toughest first-round matches I've ever played," Williams said. "I just wasn't as aggressive at the end as I was during those games.
"She started playing better. I made a few errors but for the most part, I still was going for everything and was able to close it out."