Correct, it was G-BMLP. This is not a photo of that plane but a similar one which describes the reason for the hump, it was indirectly a part of a JATO system…

Yes, that’s right. G-BMLP was ex XA-CUE of Mexicana who, over the years, operated a number of airliners equipped for rocket-assisted takeoff from ‘hot and high’ airfields.

The ‘hump’ was local fuselage strengthening, installed because it was felt that it would be a bad thing for the RATO ‘bottles’ to actually overtake the aircraft in flight…. 🙂