Asked by west London Labour MP John McDonnell whether he would rule out sanctioning a new runway while he was prime minister, Mr Cameron said he would "not be breaking my manifesto pledge".
Labour MP David Hanson has a ten minute rule bill requiring candidates in elections who stand as independents to declare if they are members of political parties - his Local Police and Crime Commissioner is Winston Roddick, a Liberal Democrat member who ran as an independent (although there was no particular secret about his party involvement).