Royal Mail said on their website it was to ensure items in the system cleared US customs before the tariffs are put in place, as tariffs have to be paid prior to items entering customs. They are setting systems up, but can't risk pre-tariff mail being refused because it was delayed reaching the US.

Sorry, should have been clear about which “this government” :)

You were clear. They left everyone with little time to prepare. Organisations like Royal Mail will have things in place, as they are using similar systems to EU VAT. I am wondering how prepared US customs are, as they will need to track parcels and check the tariffs have been paid.

It just so depressing that serious organizations around the world have to accommodate the mad whims of this US government, which can change any day.

That sums things up beautifully!