It’s not often that there is good news on the fares front, but TfL have corrected what I suspect was an error in the off-peak single fare between zones 5-7. It was £1.90 and is now £1.80, the same as zones 5-8 and 5-9.
This affects singles between Harrow & Wealdstone or Headstone Lane and Carpenders Park, as well as stations between Harrow-on-the-Hill and Uxbridge or Pinner to Rickmansworth, Chorleywood, Croxley and Watford (Met).