I do not underestimate " and you do not underestimate " the difficulty of getting towards the figure that we need. What I do not understand is why you have signed up to a goal that falls so far short of it. The suspicion must be that you do not want to sign up to a needs-based goal because of the gap that would be revealed and that your opponents will be able to say you have failed.
Surely it would be better and more honest to draw a clear distinction and say "That is where are heading to, now let us see how far we can get in terms of my own planning powers and in terms of public subsidy". Why are you signing up to a goal that is below what London needs?