This section of Derny Avenue was tagged with sidewalk=left shortly after it opened in Summer 2019, see https://www.openstreetmap.org/changeset/72642748 

There's also Mapillary imagery here https://www.mapillary.com/map/im/wYsNUSk86EI090-0Ff7DSg

It will be updated as Chobham Manor Phase 3 nears completion.