From the pics on TV it looks like its under door 2R. Theres a "strake" there to blend the fuselage with the root of the leading edge. I recall catering trucks regularly used to thump that area. The company (BA) put 2 red vertical stripes on the strakes to try and prevent this. Maybe it got thumped/damaged/punctured (and nobody owned up to it) the structure consequently weakened, which then failed when the pres diff went up.....who knows? anyway just a thought....apologies if this has already been mooted, can't read thru several pages of posts already...cheers.