Long-distance Clara: London's longest bus route London's longest bus route is the X26 from Heathrow to Croydon. It's 23.75 miles (38.22 km) long and it can take more than two hours to travel the full distance. The next longest is a night bus, the N89, from Erith to Charing Cross, at 23.3 miles (37.5km) long.

The longest bus route in London by distance is route X26, which runs from Heathrow Airport to Croydon Town Centre.

Here are the key details:

• Length: Approximately 23.75 miles (38.2 km).
• Journey time: Around 2–2.5 hours depending on traffic.
• Route: It passes through several boroughs, including Hounslow, Kingston, Sutton, and finally Croydon.
• Operator: Transport for London (TfL), operated by Abellio London.
• Frequency: Generally every 20–30 minutes.

Historically, route X26 was an extension of the old 726 Green Line coach service, and it remains the longest single bus route entirely within Greater London.

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Honorable mention:
- Route 166 (Croydon to Epsom) is also long, but part of it goes outside London into Surrey.
- Route 607 (Uxbridge to White City) is an extended commuter service, but shorter than X26.

So, if we’re talking purely within Greater London, X26 holds the record.