And this is why Starmer isn't being 'bolder', for those of us who were wondering.
The rapid expansion of ULEZ to the suburbs is a bold policy. Everyone knew it would be controversial but Khan went for it anyway because it has already been shown to be highly effective (London's air quality has improved faster than anyone thought possible since the earlier expansions of ULEZ).
The result of this unequivocally sensible policy? Of a politician taking bold but effective steps to improve public health and quality of life? Labour lose a winnable seat.
Politics isn't fair. Starmer knows it.