Congratulations - that is a amazing achievement.
While I would never call myself a marathon runner, I did finish the London Marathon three times, with the first being 1983 and the last being 1996 - long time ago now.
Funnily, as a youngster I was a 100-200 meter schoolboy level runner, then in 1982 a friend gathered five entries to the London marathon for a children's charity and said " Pete, you were a runner, come and help the kids out".
From that day forward I started pounding the streets, thighs shrunk and knees and ankles gradually eroded, remember the shoes we ran in in those early days were not impact friendly

But I ran everywhere, my first ever internet moniker done by a friend who showed me what to do in an internet cafe, was Forest Gump, he picked the name not me.
I always found it the most relaxing time of my day, the easiest way to see any city I arrived in, and to clear jet lag. I am 63 now and the injuries are taking serious toll, but then at 27 years old I was told to stop running by doctors, so I have lasted a little longer than expected. My time of pounding the streets as a form of relaxation, may well be on their last legs - pun intended . But, like any drug, I will always have a hankering to do one more great long run, even if its only destined to be in my dreams/memories
Congratulations again !