London Main Drainage Diagram

Doctor spreads the diagram on the ground beside the airplane. He traces London's sewer network, jabbing at the main flood relief sewer under Vaughn’s warehouse. Brigadier questions water levels; Isobel calls it fantastic; Turner demands evidence; Jamie listens as the group clusters close, weighing Cybermen infiltration risks.

2 appearances

Purpose

Illustrate sewer tunnels as Cybermen infiltration route to Vaughn’s warehouse

Significance

Serves as visual clue exposing Cybermen sewer hideout, counters UNIT skepticism, pivots discussion from doubt to tracing radio signals

Appearances in the Narrative

When this object appears and how it's used

2 moments

S6E15 · The Invasion Part 5

Doctor reveals Cybermen sewer threat

The Main Drainage Diagram is the visual centerpiece of the Doctor's revelation, spread dramatically on the aeroplane's exterior as he traces London's sewer network with his finger. The diagram serves as both a clue (revealing the Cybermen's likely infiltration route) and a tactical tool (pinpointing the main flood relief sewer beneath Vaughn's warehouse). Its physical presence—jabbed at, gestured toward, and pored over by the group—embodies the Doctor's deductive process, while its technical accuracy (noting dry tunnels) counters the Brigadier's initial objection about water. The diagram's role is narratively pivotal: it shifts the group's focus from abstract warning to concrete action, as the Doctor uses it to justify his demand for the transistor radio and IE equipment.

Before: Folded or stored in the Doctor's possession, unused until this moment.

After: Spread on the aeroplane's exterior, marked with the Doctor's finger traces, now a reference point for the group's next steps.

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S6E15 · The Invasion Part 5

Doctor traces Cyberman signal through Jamie’s radio

The London Main Drainage Diagram is spread on the ground, serving as the visual centerpiece of the Doctor’s argument. He uses it to illustrate the sewer network beneath London, jabbing at the main flood relief sewer under Vaughn’s warehouse to emphasize the Cybermen’s likely infiltration route. The diagram functions as both a tactical tool and a symbolic representation of the Doctor’s urgency—his finger tracing the tunnels mirrors his insistence on immediate action. Its presence grounds the theoretical discussion in concrete geography, making the threat feel tangible.

Before: Spread on the ground, visible to the group, marked with the Doctor’s finger as he traces the sewer routes.

After: Likely rolled up or set aside as the group shifts focus to the transistor radio and IE equipment, but its information remains critical for the next steps.

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