IMO, their consideration was totally flawed, they really don't have a clue as to the meaning of the signs.
It is NOT a Give Way. As they foolishly state, Give Way requirements apply ONLY at junctions, NOT Give Priority lengths of road and therefore motorists are NOT required to act as if it was a Give Way NEITHER may their actions be judged against these.
As they referred to the Traffic Signs Manual, so shall I:
To give greater emphasis to the sign to diagram 615 [the give priority sign] and to indicate the place at which vehicles should wait, the Give Way line to diagram 1003A (S9‑6‑3) may be used. The marking to diagram 1023A (S9‑6‑4) may also be provided, but not the upright sign to diagram 602 (S9‑2‑2)[an actual Give Way sign], which is prescribed for use [means it may only be used at] only at junctions or level crossings. When used in conjunction with a Give Way line, the sign to diagram 615 [the Give Priority sign] should normally be sited about 1.5 m before the marking.
In Lambeth's case they've put the line BEFORE the sign which is the other way round!
Ho hum.