Poplar

Poplar was located in London, (TV: The Bounty Hunter) in the borough of Tower Hamlets.^[1]

Poplar as seen on a digital map of London. (TV: The Bounty Hunter)

It appeared on the Department's digital map of London in 2050. (TV: The Bounty Hunter)

Footnotes

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The location of Tower Hamlets on Mr Smith's map. (TV: Revenge of the Slitheen)
The map of London boroughs in Revenge of the Slitheen shows a bend in the River Thames between Southwark and Tower Hamlets. The same bend appears in the map from The Bounty Hunter. This definitively places Poplar in London Borough of Tower Hamlets.