Move Calendar to new account

For various reasons, I need to move a calendar from a Mac running High Sierra to a new Apple ID account. (FWIW, it's synced to iCloud and this is also synced to an iPhone and an iPad.)

I've tried [Calendar] File>Export>Calendar Archive... and then Importing the resultant file on an different Mac that's signed-in to the new Apple ID but only a single subscribed to calendar is imported.

Before I start exporting all the events using AppleScript, can anyone help please? (I have a single user calendar to deal with that contains, I suppose, a few hundred events and some dozens of reminders.)