Done.

While I agree that a right turn is compulsory at the traffic lights, I'm not convinced that the left turn before the lights shouldn't permit a routing from Temple Avenue on to the Blackfriars Underpass. Although Streetview shows the arrows for traffic on the Embankment for continuing straight or exiting left, there's no signage to say that you can't turn left from Temple Ave then filter right onto the Underpass. Google Maps shows that clearly as a possibility, which no doubt means that using Google Maps for navigation would make use of that route.

I don't know that particular junction so I wouldn't want to implement it with wider consultation.