@ a year or so ago, BA upped the Club Europe/World allowance up to 18kgs per pax - I believe the max for 1 bag in that allowance is 9kgs.
I agree with the comments on safety made above and, whilst most aircraft from 737 upwards have been or were already modded to take this wieght/bulk, try making it work on an ATR or Dash 8...!
FO
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