PINNER (15 miles): I've been travelling through the affluent suburban fringes of northwest London, along green avenues lined by bright brick villas and mock Tudor domestic castles. Very few of these would have existed 100 years ago, just the odd village and farmstead along the way. But the Metropolitan Railway had just penetrated peaceful Ruislip and sleepy Eastcote, and the residential explosion was about to begin. Now the hedges along the marathon route are well-trimmed privet, not brambly bushes, and the grass is millimetre-perfect lawn, not bovine meadow. Residential nirvana, for those lucky enough to be at home today, is sitting on the back garden patio under a fringed parasol, sipping iced Pimms or an Earl Grey. Well-behaved sons cycle down to the park with fluorescent cricket stumps packed in their rucksacks, while dainty daughters in flowery dresses ask Mummy politely for an ice cream. As an Eastender used to bustle and densely-packed grime, I find the affluent atmosphere alien and alluring. Pinner is as far north as the marathon route extended. I fear it may be downhill from here on.