The Lease reserves the right of the Landlord to take possession of the property if you do not pay ground rent, service charges, any administrative charges or otherwise breach the Lease.
This is called Forfeiture.
Forfeiture applies whether payment has been demanded, or not.
If this course of action was taken by the Landlord, your lender will be very concerned since the property is their security.
Your debt to your lender remains payable and you will be pursued for it.
Best not to breach the Lease terms.
Read more from Mail Online here on the subject of Forfeiture...