Let's have a full AND proper investigation, please.
It is, perhaps, unsurprising on such a Forum such as this where pilots discuss amongst pilots, that there should be an obvious lack of consideration on the event-matrix that underpins this event and the ramifications, thereof.
As I write, the names of the 3 pilots in this event are not in the public domain and my thoughts are based (as are all others expressed by others in this thread), entirely on the allegations cited in the media being true including and not restricted to the allegation that the 'drunk' pilot was indeed drunk in the normal meaning of the word.
I would suggest that there is a bombproof construct that shows the 2 other pilots covered up for the 'drunk' pilot which would automatically make them accessories to what the man in the street would regard as an extremely serious, life-threatening, crime. Flowing from that, BA should not have allowed ANY of the pilots (not just the 'drunk' pilot) continue on their rostered flight.
For the construct to work, the following 3 criteria must hold true (1) neither of the other 2 pilots who continued to operate to Mauritius can have a sense of smell any worse than the person who reported the 'drunk' pilot (this can be tested and there are potential medical implications) (2) the reporting of the 'drunk' pilot would have to have been done by someone other than the 2 other pilots (3) the 'drunk' pilot could not have attended the washroom between the end of pre-flight briefing and passing through security on the way to the aircraft (CCTV) which is the only place he could have consumed alcohol after briefing and before entering the aircraft.
If all the criteria stated above are satisfied, I would not be sleeping too well I were either of the other 2 pilots or the senior-most BA manager dealing nor, indeed, if I were BA itself. Alternatively, if the criteria are not met, then everyone should breathe a bit easier.
I am sure that a thorough investigation into the above will be conducted by Sussex Police and that is surely what we all want in the name of passenger air safety.