I don't think you need roller-skates but on the other hand, a leisurely meal and a stroll to your gate is probably not advisable either!
The link below states you should allow 60 minutes but based on personal experience, I would suggest that is for a very inexperienced traveller as I have colleagues who do it in around 30 minutes. Anyway, if it's BA from end-to-end they should look after you - possibly
BAA Heathrow: Terminal 5 International Connecting to Terminal 5 Domestic