The LNER train was travelling from the Capital and heading across the border when the announcer reminded passengers the mask rules.
Masks on trains are only required in Scotland due to coronavirus guidelines, but not in England.
The announcement said that travellers should continue to wear masks due to “Queen Nicola” and that after Berwick "it's everybody for themselves and hopefully some common sense".
LNER have been contacted for comment.
Scottish Government guidelines state that masks should still be worn in indoor, public spaces including hospitality and transport.
A statement on their website adds: “It is recommended that you wear face coverings outdoors in crowded spaces and where it is not possible to keep a safe distance, such as at the school gate or at the entrance to a building.”