It is the city where he made his name, and now Mo Farah is ready for another landmark moment in London. In the space of just over two hours on Sunday, the direction of his life could change forever.
'It is something I am going to find out if I can do or not - and that's what I wanted,' said Farah of his much-anticipated marathon debut. 'I wanted to test myself. I know with my confidence on the track I should be there but at the same time the distance for me is a challenge. It's going to be an incredible race, whatever happens.'
Farah, 31, has grown into one of the best distance runners of all time. Of that, there became no doubt when he won the 5000m and 10,000m at last summer's IAAF World Championships in Moscow, becoming only the second man alongside Kenenisa Bekele to complete the double-double after his glory over the same distances at the Olympic Games in London a year before.
If, by design more than ambition, he is matching everything Bekele does, then the omens are good because last Sunday in Paris, the Ethiopian won on his marathon debut in a stunning 2:05:03, a course record.
But, as Farah has been told, there is nothing like the pain that he might feel from the 26.2 miles in front on him on Sunday in the Virgin Money London Marathon in a race featuring a field of the highest class.
Farah meets Wilson Kipsang, the marathon world record-holder with 2:03:23, his Kenyan teammate Emmanuel Mutai, who holds the course record of 2:04:40, Uganda's Stephen Kiprotich, the Olympic and world champion, and Ethiopia's defending champion Tsegaye Kebede.
There is one time that Farah is looking towards - that of the British best of 2:07:13, a mark that is in its 29th year, set by Steve Jones in Chicago.
'Hopefully I can break the British record and we will see what comes with it,' said Farah, who has fully recovered after collapsing at the end of last month’s New York Half Marathon where he finished second.
The outcome of Sunday's race could decide where Farah goes not only for the rest of this year, but also the rest of his running career.
Victory could mean a serious progression towards the Olympic marathon in Rio in 2016 and, equally, he might decide to aim for the event at the European Athletics Championships in Zurich in August.
Debut marathons bring so much of the unknown, and Ethiopian Haile Gebrselassie, the former world record-holder, is fully aware of the spotlight that will be on Farah while realising how much the huge crowd will have an impact, both ways.
Speaking to Sky Sports, Gebrselassie said: 'I remember in 2003 when Paula (Radcliffe) broke the record, there were so many people in the street to support her when she ran that time.
'But there is also a disadvantage sometimes, as it is a lot of pressure. When you have lots of people expecting something from you, the pressure is there.'
Yet pressure is the one area where Farah seems to thrive.
In 2012, his bid for the 5000m and 10,000m double at the London Olympics was one of the constant stories of the summer, a running theme which followed Farah all the way to the start line.
But he delivered, and in style too, as he became a household name.
Now he is back in the English capital, and will it be his moment again?
“As a young boy growing up in London it has always been my ambition to run the London Marathon,” said Farah. “And to be able to make my marathon debut in my home town is very special.”