Richmond Park is 2,500 acres of ancient parkland where red and fallow deer roam entirely unbothered by the fact they're inside a major capital city. In autumn especially, it's one of the most atmospheric places in England, misty mornings, stags, centuries-old oaks.
Cycle through it, walk to the Isabella Plantation, climb to the top of the hill for a Kingston skyline view. It's what "escaping London without leaving London" actually looks like.