The first part of our delay was no aircraft departure manager, so we couldn't board, eventually they found one so we did start boarding about 15 minutes after the scheduled departure. The next delay was the tug, or the lack of one, so we waited for 90 minutes for the tug to finally turn up and push us back. In the meantime it turns out that the airbridge had scratched the plane, so that had to come back so the engineer could inspect it and pass us fit to fly, it was just a scratch. That didn't matter in the end as we still didn't have a tug. Then finally it took over 25 minutes to taxi to the end of the runway, which considering we were at T5 C gates and we were taking off to the east it is a pretty short taxi. Consequently we arrive 2 and half hours late in Chicago at 8:45 pm, everyone misses there connection and about 50 people didn't get their luggage either. BA at it's best.
The flight itself was very nice, I even slept for over 3 hours.