my mum has run the london maraphon a few times,she looked absolutly fked by the end lol but then she is 57, i think she did it in 3hrs 40
my father in-law also run it ,im not sure how fast he did it in as i didnt go but he reassures me he stopped in the pub for a guiness on the way round lol
anyway i couldnt run that far myself
10 minutes on the running machine is enough for me, so big respect for doing it
good luck