Canary Wharf is at Mile 18, and to be honest I can only vaguely remember running through it. I'd changed trains there earlier in the day and I remember thinking "oh I was walking here a few hours ago," but that's it. I'm not even in the photo, this is just a photo from the London Marathon website, which says:

"Formerly one of the busiest docks in the world, Canary Wharf became the UK’s new financial hub in 1991. 

The 97-acre commercial estate is home to a glittering array of skyscrapers, including One Canada Square, which was the tallest building in the UK for two decades before being surpassed by the Shard. The area was given its name when fruit grown in the Canary Islands started arriving into the docks during the 1930s."