MP's have left their Party since time began; Churchill moved backwards and forwards from the Conservative Party and, if people feel so strongly that they are in the wrong party, then you cannot make them stay.
If Quentin really came to the view, two years after having been re-elected as a Conservative MP, that he was no longer at home in the Party, then he is entitled to leave it.
What I find objectionable is his timing and his language - allowing himself to be used as a pawn by the Party he has opposed for twenty years, and seeking to damage the Party that nurtured him by attacking it in language that has overtones of Labour Spin.
The more honourable course would have been for him quietly to leave the Party and to sit as an Independent MP. If he had done that, Quentin, who was a friend of mine, would have remained a friend.
However, now that he has done what he has done, I am not so sure.