Does violating Covid lock down and Tier restrictions meet rule 7a section 8

Possession - Section 8 and Section 21

About the Tenancy
The tenant has an Assured tenancy ending on the 31/03/2021 in a property located in East London.
The tenant is in a 6 room HMP property with 4 other tenants (5 tenants in total)
During the national lockdown we issued a notice to all our HMO tenants that they "must not meet socially indoors with family or friends unless they are part of your household or have formed a support bubble with them." This email and letter was sent to all tenants in March, November and Late November when London was placed in Tier 3 Restrictions which includes restrictions on indoor gatherings.

Although we provided the other tenants information on what they can report to the police in relation to covid violations to our knowledge it has not been reported to the police.

A number of tenants reported a violation of the above rule to us. We issued the tenant with a written warning for violating a term of the tenancy. We also witnessed a violation against having visitors.

The tenant has continued to violate the rule, the other tenants have reported the violation again with associated noise and disturbance.

Can we issue the tenant with a Section 8 notice under rule 7a. Or can this be done only after it has been reported to the police by other tenants.