# What moves through the gateways

> By value, Heathrow is one of Britain's biggest ports.

- Category: Money
- Cadence: monthly
- Status: Published on a monthly cadence.
- Dataset key: `trade-by-port`
- Source: [HMRC uktradeinfo](https://www.uktradeinfo.com/)
- Licence: Open Government Licence v3.0 — [terms](https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/)
- Canonical page: [https://londongraph.com/g/what-moves-through-the-gateways](https://londongraph.com/g/what-moves-through-the-gateways)
- Machine-readable record: [https://londongraph.com/data/what-moves-through-the-gateways](https://londongraph.com/data/what-moves-through-the-gateways)

## Methodology

Declared value of goods through London's ports, monthly, from HMRC's Overseas Trade Statistics: Heathrow, London and Tilbury, and London Gateway. Goods only — London's economy exports services, which are invisible here. Heathrow dominates because what flies is small and expensive. City Airport is in HMRC's port list and is deliberately absent: it reports effectively no goods, and a flat line at zero is noise wearing the clothes of information.

## Visualisations

- [Trend](https://londongraph.com/g/what-moves-through-the-gateways): By value, Heathrow is one of Britain's biggest ports.
- [Small multiples](https://londongraph.com/g/what-moves-through-the-gateways?view=small-multiples): Give each series its own aligned panel.
- [Change](https://londongraph.com/g/what-moves-through-the-gateways?view=change): Show the change from each preceding published period.
- [Share over time](https://londongraph.com/g/what-moves-through-the-gateways?view=share): Normalize each period to show how the mix changes.

## Citation guidance

Attribute the original publisher named above and identify LondonGraph as the visualisation and methodology layer. Do not describe live values as a historical census, and do not present placeholder values as observations.