Was wondering the same thing myself - friend is meant to be onboard and I promised to look out for 002 going over Chelsea.
Rang BA, and got transferred from the auto operator to a real human being (!), and was told that 002 will take off from JFK @ 21:30 and land at LHR @ 07:45 tomorrow morning (6th Oct). No reason was available...
It's a shame for the flagship of the BA fleet to go out on a series of operational issues like this.