It depends if all the facts stated in this post are accurate. I know of similar situations where other parties have been in occupation and 146 procedure was accepted by county court. It depends upon whether the occupier is acting as an employee of the original tenant or whether they're running things as if it were their own business. Surprisingly, particularly if its in the same town, word gets around quite quickly.
Have you had any discussions about assigning the property?
The opinions I give are simply my opinions and interpretations of what I have learnt, in numerous years as a property professional, I would not rely upon them without consulting with a paid advisor and providing them with all the salient facts BSc (Hons)