The boss of M&S was using Percy Pigs as an example of a situation in which it was not yet clear whether a tariff needed to be paid.
The sweets are manufactured and packaged in Germany and then shipped to the UK – no tariffs are payable because of the trade deal.
They are then taken from the M&S warehouses and exported to stores in the Republic of Ireland, which is part of the EU.
Now, this is the complicated bit. Because they have left the EU and not been processed enough to count as being made in the UK, it may be that a tariff needs to be paid to get them back into the EU, despite them having been made in the EU in the first place.
If they had been unpacked and put on a cupcake, for example, there would be no tariff because they would have been transformed, but just storing them in the UK is not enough.
Lions with flamethrowers for the lot of them.