I am a good boy, and would never have to appear in court. I have no idea what the British law are around such devices, but have no interest in finding loopholes.
My posts are instead about the positions made by other posters, who have said that the BA rule may well not affect anything but should be followed blindly as they have been made and agreed by experts.
The law is quite clear that British Airways must abide by the CAA regulations currently in force. That means that British Airways staff must be seen to uphold the CAA regulations at all times, and actively enforce them.
Whilst it may well be true that electronic items are less risky than they were when the CAA Regulations were last reviewed, until such time that the CAA has relaxed the regulations (British Airways still retains the right to refuse to accept any recommended relaxation if it so chooses) then we have to accept that the rules exist and abide by them.
I am not entirely convinced regarding the claims that "modern electronics are safe" - in fact, given the fact that nearly every passenger on an aircraft will carry at least one electronic gadget as well as at least one mobile phone, the Electro-Magnetic Field throughout the aircraft cabin and the potential for mass interference is incredible. Although the airframe is, in itself, a very efficient "Farraday Cage" designed to protect against lightning strikes, electronic transceivers seeking a base station will amplify the aircraft's attraction to a lightning bolt. Anyone who has sat through a lightning strike in flight will know how frightening that is!
Until such time as the regulations are changed, we must all of us abide by them without question. Whilst I do have a military background, that is entirely irrelevant.
Everything one buys has a Terms and Conditions of Sale. British Airways has its own Terms and Conditions. If you can't agree with them, fly with another airline who suits your purposes.