This example displays a choropleth map of the United Kingdom’s administrative districts, rendered as an SVG using React. It shows the geographic boundaries of English local authority districts, with each region colored green and outlined in pink, red upon hover. The code uses D3 v5’s `geoMercator` projection and `geoPath` to generate the map from TopoJSON data loaded via `d3.json`, while `topojson.feature` and `topojson.mesh` extract land polygons and interior borders.