Grace is not a quality often associated with Donald Trump. So it is predictable that he would prefer to spend a day at his Florida golf club rather than be present in Washington to welcome the American young people in the March for Our Lives.

Had he done so, as surely most of his predecessors would have, he would at least have demonstrated some empathy for the victims of recent shootings. It is indefensible that there was no official recognition of the march. A bland statement by the administration’s deputy press secretary was not good enough.

Still, that did not deter the half-million protesters in the US capital, nor those on the 800 sister marches across America and the world. Rallies in London and Edinburgh showed solidarity with the victims of gun crime and for the efforts of the worldwide movement to make firearms harder to obtain, most obviously in America.

Unlike the demonstrations after many previous school and other massacres, those at Parkland, Florida, have maintained their momentum, spread nationally and internationally and have a clear political focus. While the National Rifle Association is a famously tough and powerful interest group, the will and the sentiment of the many millions who feel that America needs to make its schools and streets safe is making itself felt. The anti-gun lobby is getting organised.

Thus it is that even the stubborn President Trump has chosen to restrict the supply and possession of “bump-stop” mechanisms that convert semi-automatic rifles into machine guns. Of course, the President couldn’t resist tweeting that he was reversing an Obama-era measure, but no matter. The Attorney General Jeff Sessions has taken the initiative, and it is something no one expected from this White House.

It is an important moment. It shows that even a president elected on a pro-gun agenda can be made to shift policy. It proves once again that the US constitutional right to bear arms is not, and never has been, absolute. Weaponry is controlled and it can be controlled some more. A more determined president and a more responsive Congress could do much more.