Originally Posted by
Audio
I cannot understand why a change of departure time of 5 min could cause so much grief.
If it is me, I would just chance it after all, in reality, flight delay as much as 30 min is quite normal. I have been on delayed flight and I was at the transfer desk less than 60 min before my next departure (separate booking) and my baggage and I managed to make it.
As the OP said, the ticket is no longer a valid ticket because it doesn't meet the minimum connection requirements. Furthermore, in this case the BA flight is at the start of the day so more likely to depart on time, whilst the CX flight lands at a busy time and so is frequently delayed. In fact I have often been on CX251 (the flight the OP wants) and noticed the CX255 landing earlier.