The London Marathon is on a Sunday. Brighton is 55 minutes south by train. These two facts have been combining in runners' minds for decades, and there is no particular reason to resist the logic. Southern Railway runs direct services from London Victoria and London Bridge throughout the day; trains leave every 15 to 30 minutes and the fare is around £10 to 15 single if bought on the day. Brighton station sits at the top of the hill above the seafront: the walk down Queen's Road and West Street to the promenade is ten minutes of gentle, welcome downhill. The only gradient of the whole day is in the right direction.
April on the south coast sits at 10 to 14°C with a sea breeze that makes it feel like more. Bring a layer. The kind of April day that photographs well, clear sky, low light, the chalk cliffs visible along the coast, is common enough to be worth hoping for.
A timing note: the Brighton Marathon also runs in April, typically one or two weeks after London. If your day trip falls on that specific weekend, the seafront will be busy with its own race infrastructure. Check the Brighton Marathon date for your year.
The Promenade
The Brighton Promenade is the primary post-race asset: a wide, flat tarmac walkway running along the seafront for several kilometres in both directions. Walk west toward Hove, quieter, more residential, the beach clubs and stalls thinning out as the Adelphi and the Brunswick terraces appear. Walk east toward the Marina, past the remains of the West Pier, its Victorian ironwork rusted and partial in the water, and the Palace Pier extending into the Channel on its 524-metre iron legs.
Brighton Palace Pier is exactly what it looks and sounds like: brash, fun, and exposed to the full force of the Channel wind at its seaward end. The amusements and rides operate from Easter; in April they are running. Walk to the end and back: about a kilometre each way on flat decking, sea visible on all sides. The fish and chip kiosks at the pier entrance have been serving battered cod since before most of the surrounding buildings were standing.
The Lanes and the Royal Pavilion
The Lanes, the compressed 17th-century alleyways between the seafront and North Street, are the most rewarding hour of a slow April afternoon in Brighton. The original street plan of Brighthelmstone, the fishing village that predated the resort, these lanes are narrow, occasionally less than two metres wide, and contain a remarkable concentration of independent jewellers, antique dealers, and coffee shops that are specifically not chains. No particular gradient. No required objective. Take whichever turn looks interesting.
The Royal Pavilion, George IV's seaside palace built in a fantasy of Indo-Saracenic domes and minarets between 1787 and 1823, is five minutes north of The Lanes. The exterior, visible from the surrounding gardens (free entry), is the experience: the cluster of onion domes and minarets rising above the Regency terraces of Brighton is one of the more surreal architectural moments in England. Interior tickets are around £18 if you want the Banqueting Room, the Music Room, and the chandelier modelled on a water lily.
Where to Eat
Riddle and Finns on Meeting House Lane, in The Lanes, serves local Sussex oysters and the day's catch in a bare-brick wine-bar setting that makes seafood feel appropriate rather than aspirational. The oysters at the bar counter with a glass of Muscadet is the correct order for a Sunday afternoon after a marathon.
For something more casual: The Bankers fish and chip shop near the West Pier does traditional battered cod in paper, which is best eaten on the beach (pebble, not sand: Brighton never apologises for this) while watching the Channel and keeping a peripheral eye on the seagulls.
Getting Back
Southern Railway runs back to London Victoria and London Bridge throughout the evening. The last trains are late enough that there is no urgency. A return ticket booked on the day at the station is the simplest approach.