Directions:

Hop on a direct train from London to Brighton from either Victoria Station or London Bridge. The journey is just over an hour if you make sure to take the fast train.

Start your walk from Brighton seafront, heading east along the Undercliff Walk from Brighton Marina to Saltdean. For about 3 miles, the path runs along the seawall with the looming white cliffs on one side and the shingle beach on the other.

The trail passes the Greenwich Meridian Monument, marking the point where the Greenwich Meridian Line crosses the English south coast. You then climb along the cliff tops for a few miles until you reach Newhaven, an old port town, which may be a little lackluster overall, but has Newhaven Fort, which is worth a visit, and Newhaven Harbour, where you need to head to cross the River Ouse.

Continue along to Seaford, passing the Seaford Head Nature Reserve, coming to Cuckmere River and Cuckmere Haven, where you begin to follow a riverside path along to Exceat Bridge. If you want to break your journey with an overnight stop, Seaford is a good place to rest for the night.

Continuing on, follow the signs to the Seven Sisters Country Park, which will bring you back to the coast, affording excellent views of the mighty Seven Sisters Cliffs. From here, pick up the South Downs Way path, heading east to Birling Gap, where you can stop off at the Belle Tout lighthouse for a cafe pitstop and stunning sea views. Then head in an easterly direction along Beachy Head, the highest chalk sea cliff in Britain. From Beachy Head, descend into Eastbourne, going along the pebbly beach before finishing at Eastbourne Pier. Catch a train back to London, which has a minimum 1.5-hour journey time.

Sources: https://www.carfreewalks.org/walks/893/apiertopierwalkineastsussex http://www.gps-routes.co.uk/routes/home.nsf/RoutesLinksWalks/brighton-to-eastbourne-walking-route