My return journey after landing at Heathrow T4 was off-peak but I decided against travelling all the way by rail back to Willesden Green (with my Zones 1-2 Travelcard and National Railcard discount), as I was pulling heavy luggage and wanted to take a bus from Acton Main Line to get home. I paid £4.60 for the “privilege” as the journey was in Zones 6-3, totally outside my Travelcard coverage.