Notice of eviction served to me by fake landlord

I have a rented flat in Kolkata where I have been living from the past 26 years. It is a three storied building with around 15 tenants in it. When I had taken the possession of the flat in 1991 I used to get a bill for my rental from a person claiming himself to be the landlord. Ever since 2005 when the so called landlord completely started over looking the building to an extent that even the basic maintenance of the building was not done by him I along with all other tenants stopped paying him the rents and had initially started paying toward the building association , which was setup by my fellow building tenants, as it was found in the KMC records that the property belonged to Boo Ali Wakf Board and the fact that taxes worth lacs were due in KMC for our building. However keeping things in mind that I had a good relationship with the guy who claimed to be the landlord I kept paying him as well as I was never interested in getting into any friction with anyone for a small sum of money. I kept paying him till 2015 when he suddenly refused to accept the rents putting a demand of increasing the rent by 5 times. As this was something I felt is completely baseless as he had no role any more in the maintenance of the building I refused to accept this and waited for him to come down to a settlement. After a couple of years went by and he did not turn, I submitted my rent in the rent control and have been paying in the rent control till date. Now recently in 2018 all of a sudden he sends me an eviction notice through his lawyer mention all possible framed clauses from default in paying rents to need of property for personal accomodation and has asked me to vacant my house in a month. Though initially I used to pay him rent and even till date I pay in the rent control on his name so what shall be mine defence in such a scenerio where he files an eviction suit against me. I have all documents to prove that he is not the owner or landlord of the premises. Kindly help with legal advice.