I think something along those lines from the outset may have done the trick but now, still with inconsistencies, I'm not so sure.
I especially loved "testing" your eyesight by driving 30 mins with the child, you were so worried about, in the car.
However, for me, the bigger story is the shockingly bad effort Boris made yesterday that lead to that performance being necessary. DC had to step up because the PM wasnt up to the job.
I think DC has probably done enough to survive, but the damage is done to Boris and the party will have him out within a few months.