Paul Corfield wrote:

Highbury to Clapham has a direct service at peak hours, backed up by a
same-platform interchange for the rest of the time.

Err it actually has a x15 min service in the peaks and x30 at all
other times since the May timetable change. Off peak I have certainly
seen people waiting for a direct Clapham train at places like
Brondesbury or Hampstead Heath.

Ah my bad. In my defence I tend to use different sections of Overground and
hadn't seen any advertising of a more frequent through service.