Southeastern are offering a 25% reduction on off-peak tickets from Sevenoaks to London. An off-peak return costs £8.45. You can only buy the tickets online – they are not available at the ticket office.
The discount only applies to rail-only tickets. There is no discount available on One-Day Travelcards. So if you will be using tubes and buses a lot (for example 4 tube journeys) once you get to London a Travelcard (£15) would still be slightly cheaper than a rail ticket (£8.45) and the Oyster PAYG Zone 1 Daily Cap (£7.00).
Similar discounts are available to some other destinations, including Tunbridge Wells. Don’t be misled by the absence of Sevenoaks from Southeastern’s advertisements: it turns out the advert only shows examples.
Update: Peter Fleming, Leader of Sevenoaks District Council, has pointed that parking in Sevenoaks is free on Saturday 6 December and Saturday 13 December – and you can do your Christmas shopping locally and avoid the Oxford Street crowds. A 100% discount sounds good to us: come on, Southeastern, beat that!