Epping Forest is the reason people keep saying London is a green city. Seven kilometres from Chingford station gets you into proper ancient woodland — hornbeam, oak, beech — with a Tudor hunting lodge, a Victorian tea room, and a pub at the far end.
Start at Chingford and walk ten minutes to Queen Elizabeth's Hunting Lodge — a 1543 timber-framed building that Elizabeth I herself probably saw. Free to enter, three floors up to the top for the long view.
Butler's Retreat next door for coffee and a piece of cake. Then into the forest proper: Connaught Water first for the easy loop, Hawk Wood for the trees. The paths are well-signed but don't be afraid to go off-piste; the forest is legally protected commons, and the way-finding is actually the point.
Climb to High Beach for the view east — on a clear day you can see the Thames estuary — and then the King's Oak pub for a pint before the walk back.
Seven kilometres, a full morning, a complete change of mental weather.