TCS London Marathon

{
  "guide": [
    "Use the three-start system to your advantage — don't fight the early crowds, settle into goal pace by km 5.",
    "The Tower Bridge surge will lift your pace 5–10 sec/km. Let it, but don't bank time — you'll need it in the Canary Wharf chicanes.",
    "Tangents matter on the Embankment — the long sweeping curves can add 100 m if you drift wide.",
    "Crowds are loud throughout. Conserve mental energy — don't high-five everyone in the first half."
  ],
  "profile": "Flat with one mild climb. Three start lines (Red, Green, Blue) merge by km 5. The course is a giant clockwise loop along the Thames, with the bridges providing the only meaningful elevation.",
  "terrain": "flat",
  "keyFeatures": [
    "km 0 — Three starts (Greenwich Park) merge near the Cutty Sark at km 11.",
    "km 19 — Tower Bridge. The single most photographed moment in marathoning.",
    "km 22–32 — Canary Wharf loop. Twisting streets, narrow turns — easy to lose rhythm.",
    "km 38 — Embankment. Big Ben in view at km 41.",
    "km 42.2 — Finish on The Mall in front of Buckingham Palace."
  ],
  "elevationGain": 42,
  "elevationLoss": 42
}