Length: 18 km (11.2 miles). Toughness: 4/10
10:05 Reigate train from Victoria (Clapham Jct 10:12, East Croydon 10:23), changing at Purley (arr 10:28, dep 10:37) onto the Tattenham Corner train, arriving there at 11:01.
From north or central London you could take a Thameslink service direct to Purley (St Pancras 09:40…Blackfriars 09:49…Purley 10:18) but note that they're not going via London Bridge this Sunday. South Londoners might be able to pick up the Caterham / Tattenham Corner service directly as it calls at almost every station imaginable after leaving London Bridge at 09:44.
Return trains from Merstham are hourly to Victoria at xx:15, plus Thameslinks via Blackfriars at xx:10 & xx:37.
You can use Oyster at both stations, but Merstham is one stop outside the TfL Zones. You'd need to buy a single to Coulsdon South if you've got a Freedom Pass or buy a Travelcard.
I was hoping that some of the fields in the First World War Centenary Wood at Langley Vale would be a sea of red as they were a few summers ago, but sadly the poppies have all but disappeared. However, there will still be plenty of other wildflowers to brighten up the new plantations.
The suggested lunch pub is the Blue Ball in Walton on the Hill, with the Village Café as an alternative and benches next to Mere Pond where you can munch sandwiches. If you'd prefer to do more than half the walk before stopping you could carry on for another 50 minutes to The Sportsman on the other side of Banstead Heath. The Junction 8 servery at the Reigate Hill car park is available for a mid-afternoon reviver, and The Feathers is a stone's throw from Merstham station.
You'll need to bring the directions from the L=swc.398.a