Hate to tell you Brian but I'd be surprised if it was a 747 on LHR-ORD .... we normally fly 777 s on that route.
Also would suggest that you apply for BA Exec card and onec you've got the no. call BA up and get the card added to your booking so you get the mileage on a journey like the one you have ...it won't be loads but its something for nothing as you've already booked.
rgds
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