Those GPMs are one of the reasons that the myth of LHR service "quality" has been allowed to prosper. It would be difficult to imagine a customer feedback system more open to abuse.
The forms are handed out and collected by the self same crew that are the subject of the report. In other words they know exactly who has a piece of paper that could drop them in the do-do. They also have the opportunity to read the form before it is submitted to the company. The system can easily be "massaged" to give positive feedback.
A far more accurate measure of the "quality" of the service on board can be found in the various passenger chat forums. The picture there is far less rosy, with BA (and in particular LHR) scoring no better, and in many cases worse, than any other long haul scheduled operator. You know, the ones who get paid "slave wages".
