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It's the little feeder cycle path crossing High Holborn opposite the Princess Louise.
google streetview and enhance
Given the way the traffic lights are pointing (only visible/relevant to cyclists using that feeder cycle path) I'd guess you'd be hard pushed to claim that you thought it/they didn't apply to you.
On streetview the manhole cover just before the second traffic light (at the start of the cycling contraflow) seems to have the remains of a white line on it, but that may have just been originally part of the 'give way' dashed lines from a time when the cycling contraflow didn't exist and the whole width of Newton St was one way.
No. The page I can't find right now (maybe it's in the history of a browser at home) made it clear that if the white line is missing and it's obvious it should be there then you've got no excuse for not complying with the red light. Probably not explaining it well enough, the web page I read put forth a much more compelling argument.