The scenario of a so called "Hard Brexit" (the United Kingdom - UK - to leave the EU with no deal*) is still a possibility. All parties involved started plans for such eventuality, including governments and authorities.
Now, the UK Government is preparing legislation to allow the continued sale of and access to medicines manufactured in the remaining EU. This will be done via amendments to the existing UK Human Medicines Regulations 2012 (HMR 2012).
The changes now planned to the HMR 2012 take into account the possibility that UK will no longer be part of the harmonised EU pharmaceutical network after the date of exit in a no deal scenario. In fact, the current rules should be transferred as far as possible to the 2019 Regulations, taking into account EU requirements. However, there will also be appropriate changes necessary for an independent regulatory authority outside the EU network. For example "UK" will be inserted before the term "marketing authorisation" in various parts. The UK government may also set out principles and guidelines of good manufacturing practice in respect of medicinal products and investigational medicinal products.
The Human Medicines (Amendment etc.) (EU Exit) Regulations 2019 are subject to approval by Parliament.
*UK would leave not only the EU but also the EU's Single Market (of which non-EU countries are also members) and the EU Customs Union (of which non-EU countries are also members).