Britain's Andy Murray marked his return to the Australian Open - where in 2019 he thought he might have to retire - with a tense five-set win over Georgian 21st seed Nikoloz Basilashvili.
Murray cruised to the first set in 23 minutes but any hopes of a routine win disappeared as Basilashvili recovered.
Momentum swung both ways before the wildcard won 6-1 3-6 6-4 6-7 (5-7) 6-4.
Murray, 34, was one of three Britons to win on Tuesday, with Heather Watson and Dan Evans also progressing.
US Open champion Emma Raducanu and qualifier Liam Broady play later on Tuesday.
Murray, a five-time beaten finalist in Melbourne, will play Japanese qualifier Taro Daniel in the second round on Thursday.
"It's amazing," Murray said shortly after winning on John Cain Arena, where he lost to Spain's Roberto Bautista Agut in 2019.
"It's been a tough three or four years but I've put in a lot of hard work to get here.
"I've played on this court many times and the atmosphere is always incredible.
"It is where I thought I had potentially played my last match but to win a five-set battle like that, I couldn't have asked any more."
Three years ago at Melbourne Park, Murray caught everyone by surprise by tearfully announcing he feared his illustrious career was coming to an end.
The hip injury that had plagued him since the summer of 2017 was debilitating and the only option left was resurfacing surgery that saw metal inserted into the joint.
No player has returned to the singles game after that operation - but Murray did later that year.
On Tuesday he played on the same court where a retirement video - featuring messages from his peers - was infamously and prematurely played after he was beaten by Bautista Agut.
Another niggling injury stopped Murray going to Melbourne Park in 2020 and last year his hopes were scuppered when a positive test for coronavirus stopped him flying out.
The venue's title has changed - renamed from Melbourne Arena in honour of the former Victorian Prime Minister - and the atmosphere was different, with only 50% capacity allowed because of coronavirus restrictions.
But the fluctuations of the match - and the associated tension for Murray fans - remained.
Murray beat Basilashvili for the third time in the past year, following a dramatic four-set victory at Wimbledon in June and a win last week in Sydney
Little troubled Murray as he rattled through the opening set, where Basilashvili's woes were summed up by an extraordinary serve that hit the racquet frame and flew upwards into the stands.
Powerful hitting is the Georgian's strength and once he managed to execute his biggest weapon, he regained a foothold in the match.
The second set saw Murray's serve broken three times on the way to the Georgian levelling.
An entertaining third set was edged by Murray at the fourth opportunity, but the Scot was pegged back again when Basilashvili started hitting lines with crunching winners to take control of the tie-break.
But, with the crowd behind him, Murray summoned the energy to win the decider. He moved into a 3-0 lead and sealed his place in the last 64 with his third match point.
Ranked 113th in the world, Murray has repeatedly said he remains confident of going deep into major tournaments once again.
Encouraging performances towards the end of 2021 reinforced that belief and he backed that up by reaching the final last week in Sydney, although he was beaten by Russian Aslan Karatsev.
Murray needed almost four hours to beat Basilashvili and there were moments after long rallies where he looked exhausted.
On his aims in Melbourne, he said: "Hopefully keep improving - there are things in my game I could do better.
"I would like to have a deep run. It's something I haven't had since I came back from injury - and I hope I can do it in this tournament."