I had faced a similar situation in Dallas when my domestic flight got delayed due to bad weather. I was lucky that my international flight also got delayed. Usually it will take 15-20 mins to travel from one terminal to another.
No, too many things can go wrong. Your flight may be late, the airlines close the door ten minutes early too. You should go in and speak with British Airways ahead of time to see if there is anything that can be done. I just spoke with Laura of costumer service and she agreed that this isn't enough time. I'm terribly sorry.
Boarding normally starts 20-40 mins before departure. Most international flights will be flying out of terminal D. There is a skylink that connects all terminals and takes about 5-10 mins to get to a different terminal. Aslong as your first flight has no delays you should make your london flight. Hope this helps.
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