Length: 14¾ km (9.2 miles, toughness 3/10), or 12¼ km (7.6 miles, 2/10) if bypassing Arundel Park at the end.
09:35 Portsmouth Harbour train from Victoria (Clapham Jct 09:42, East Croydon 09:56), arriving Arundel at 11:02.
Trains back are hourly at xx:54.
The meadows in the Arun valley are sometimes flooded in winter but two recent expeditions haven't reported any problems, so I'll take the risk of posting this Short Circular Walk from Arundel. The outward leg alternates between riverside paths and low hills on the eastern side of the valley as far as South Stoke, with its distinctive little church. This variation crosses the river here and returns through water meadows, then skirts around the Arundel Wetland Centre. There's a choice of routes into Arundel: a gentle climb through Arundel Park or a level stroll along Mill Lane.
You could stop for an early drink or pub lunch at The George at Burpham, but if you can hold out for another hour I suggest pressing on to the Black Rabbit in its enviable riverside setting at Offham. At both places you might be able to eat outside without booking, but you'd certainly need to call ahead if you want a table inside. If they each decline your custom it's not much further into Arundel, which has plenty of possible lunch and tea places. It's a ten-minute walk from the town to the station.
You'll need to bring the directions from the L=swc.100.b