Donald Trump really is a protectionist. It is more than mere rhetoric. This is the lesson from last week’s announcement that he would sign an order this week imposing global tariffs of 25 per cent on steel and 10 per cent on aluminium.

These tariffs are not that important in themselves. But the rationale used to justify them, their proposed level and duration, the willingness to target close allies and the president’s statement that “trade wars are good and easy to win” must alarm all informed observers. This action is unlikely to be the end; it is more likely to be the beginning of the end of the rules-governed multilateral trading order that the US itself created.

This may sound alarmist. It should not. True, the proposed actions target only a little over 2 per cent of US imports. If this is where they end, then the world — and the world economy — will surely take it in its stride. It is possible that, with someone as inconsistent as Mr Trump in charge, this is where it will end. But we cannot bet on it.