This route is reminiscent of the Peak District - not a comparison we make lightly. The hidden Woldingham valley is a wonder, where the cycle route through the boarding school at the valley's base is traffic free and lined with fields of cattle.
Head south through Wickham and into the lanes until you reach the excellently named Hallihoo Valley Lane. From there, descend and take it all in. It's worth savouring; escapism this good is hard to come by inside the M25.
Out the other side, there's a punchy climb with great views of Kent to the south, and a cake stop at Botley Hill Farmhouse. Loop around the far side of Biggin Hill for a return, and spin back towards Beckenham.