Terrorism prevention and investigation measures bill

My right hon. Friend is being very generous with her time this afternoon, as always, and is advancing a powerful argument. She will recall that when the Minister responded to my intervention earlier by telling me that national security would always be his highest priority, I was slightly taken aback, because I would not have doubted for a second that that would always be the case. In view of all the risks that will face us next year and the fact that an entirely new system is being introduced involving additional officers, can my right hon. Friend help me by explaining why, given a choice of dates, the Minister should pick the earlier rather than the later date to introduce his measures?