Police spotting (junction watch)

Sorry, I meant that as cyclists will constantly be using it (as the restriction makes no sense whatsoever), they'll be able to make periodic spot checks (as they are doing), but not be able to consistently enforce it. I should have said "unworkable" again, as above.

Well, they could stick a policeman there night and day to guard it if they wanted to.

This sort of pointless restriction

I don't think it's entirely pointless. Without knowing the official reason, it is a very narrow lane, and with the constant oncoming traffic on the other side, mixing buses and bikes there creates potentially dangerous situation, as it's almost impossible for either party to overtake safely.

Of course everyone could just wait their turn and not overtake, but that's unrealistic, so forcing cyclists to take the very minor detour around high holborn seems sensible to me, if it reduces the chance of accidents on that section.