Here's chapter and verse - the authority for the halting of proceedings for possession of tenanted and mortgaged properties and evictions in the form of a practice direction made under the Civil Procedure Rules 1998.
PRACTICE DIRECTION 51Z – STAY OF POSSESSION PROCEEDINGS - CORONAVIRUS This Practice Direction supplements Part 51
1. This practice direction is made under rule 51.2 of the Civil Procedure Rules (“CPR”). It is intended to assess modifications to the rules and Practice Directions that may be necessary during the Coronavirus pandemic and the need to ensure that the administration of justice, including the enforcement of orders, is carried out so as not to endanger public health. As such it makes provision to stay proceedings for, and to enforce, possession. It ceases to have effect on 30 October 2020.
2. All proceedings for possession brought under CPR Part 55 and all proceedings seeking to enforce an order for possession by a warrant or writ of possession are stayed for a period of 90 days from the date this Direction comes into force.
3. For the avoidance of doubt, claims for injunctive relief are not subject to the stay in paragraph 2.