All of it. Git yourself a London Hidden Walks book from Stanfords on Long Acre, Covent Garden.
Or just wander round Bloomsbury, Soho, Holborn, St Giles, Temple, Fitzrovia, Marylebone, The City, Islington, Highgate, Hampstead, Chelsea, Spitalfields, Chiswick, Wapping, Westminster, Clerkenwell, Bermondsey, Pimlico, Camden, Belgravia, Clapham etc etc
Perhaps Eastgermanautos could hook up with Ash
Or follow him
(He normally starts in Highgate Cemetary )
10 characters? Pile of cund.
It isn't a marathon because you don't have to run the damn thing, and you don't need three alcohol-free months of training for it, as a friend is currently enduring in preparation for the London Marathon.
We did 20 miles back from Epping and it did get a bit slow on the final haul up the Holloway Road. This one could be a bit further because the route you saw probably wen't straight down the A40, and having walked a stretch of it before it isn't a route we'd prefer to do again. So some route to the north of it will be taken. There will be an early start and many pit stops.