Are you sure that Bute Avenue is private *access*?

Looking at the Bing Streetside imagery, it's certainly privately owned (ownership=private). It does not appear to be gated and is signed as "no through road" rather than something more restrictive, so presumably residents can received visitors,  deliveries and taxis without prior permission. Perhaps access=destination would be a better fit than access=private here?

https://wiki.openstreetmap.org/wiki/Tag:ownership%3Dprivate
https://wiki.openstreetmap.org/wiki/Key:access#List_of_possible_values

https://www.bing.com/maps/?cp=51.503626%7E0.089829&lvl=21.5&mo=om.1&pi=-18&style=x&dir=83.7