Illawarra marathon man and former Lake Illawarra High School student Dr Tom Denniss hit the 13,000-kilometre mark yesterday in his run around the world for charity.
The achievement was a major milestone for Dr Denniss, who also completed his 300th marathon this week in his quest to run 700 marathons in 700 days.
His 100th was achieved on the 85th day in Monument Valley, his 200th near Mississippi and for his 300th he had the backdrop of Niagara Falls to use for inspiration.
"I passed the one-third point a couple of months back," he said.
"I am approaching halfway, which should occur next month."
Dr Denniss has almost completed the United States leg of his 29,000-kilometre global run with the final marathon on US soil scheduled for Boston on October 30.
He will then head to Chile to run over the Andes and across Argentina.
After starting in Sydney, he ran through New Zealand before heading to the United States to continue his Guinness World Record-attempt at the fastest circumnavigation of the world on foot.
Dr Denniss said he was still well ahead of schedule.
"I expect to finish [at the Sydney Opera House where it began on New Year's Eve] in September next year," he said.
"It is physically easier than I expected. The mental side is the hardest part."
Dr Denniss said one of the great things about running was that he got plenty of time to take in the scenery and think.
"I think about all sorts of things - memories of childhood, quantum physics, recalling past days on the run etc," he said.
And what keeps him going?
"The thought of running back through the Illawarra," he said.
Progress reports and images are posted every day on Facebook, Twitter and www.tomsnextstep.com website. Donations can also be made to Oxfam.