This starts along a country lane through the secluded Austin Lodge valley, climbing to the isolated settlement of Romney Street. It continues on an undulating section to a ridge with fine views of the Darent valley, from where you descend into Otford, passing its scale model of the Solar System. The village has many interesting old buildings and the full route takes you past the ruins of Otford Palace, a rival to Hampton Court in Tudor times.
For the afternoon leg follow the Shoreham directions (there is also a shorter route that passes through Shoreham). You can continue on to Eynsford with all route options.
Scroll down the walk directions page for a useful interactive map showing the various options.
Trains: Get the Thameslink 0946 Sevenoaks train from London Blackfriars, arriving 1041. Alternatively, the 0955 Ashford Intl train from Victoria, changing at Swanley arr 1023 for the above train at 1036.
Shoreham has a frequent service variously ending in Victoria, Blackfriars or London Bridge.
Buy a return to Shoreham (which is further down the line from Eynsford), or to Eynsford if doing one of the other options.
Lunch: Otford, after about 8½ km. The walk route joins the High Street opposite the Bull (01959-523198) or a traditional village pub overlooking the pond, the Woodman (01959-522195).
Tea: Shoreham has some pubs & tea rooms, as does Eynsford