I got this today by email direct from gov. Uk as I’d signed up for brexit updates
Prepare to drive in the EU after Brexit
What all drivers from the UK may need to do to drive in the EU and EEA when the UK leaves the EU on 29 March 2019.
4:53pm, 21 March 2019: Clarification that if you are travelling in the EU and EEA with a UK registered caravan or trailer, you will need two Green Cards: one for the towing vehicle, and one for the caravan or trailer
Prepare to drive in the EU after Brexit
What all drivers from the UK may need to do to drive in the EU and EEA when the UK leaves the EU on 29 March 2019.
4:53pm, 21 March 2019: Clarification that if you are travelling in the EU and EEA with a UK registered caravan or trailer, you will need two Green Cards: one for the towing vehicle, and one for the caravan or trailer