Outstanding balance claimed after 4 years later

I rented a house at Kenilworth from Mario with another signatory. This other tenant caused damages to the property and was behind on her rent payments. The tenant was, for these reasons, forced to evacuate the house. The damages were never attended to during my stay at the house after the other tenant had left. A new contract was never drafted were i would be the only signatory of the house. I later decided to move out. I gave a 1 month notice(even though the lease agreement requested 2 months notice)and Mario did not even bother to remind me it was actually 2 months that i had to serve notice. Mario and myself agreed that i would pay an undisclosed amount plus the deposit to cover the rent for the last month i occupied his premises. Mind you,i moved out 4 years ago in 2011 and i thought the case was over and done with then. Now just a moth ago in September 2015, MNeto sent letters requesting rent for the other month i did not serve as notice plus the damages that were caused by that other tenant plus 4 years worth of interest. My question is why did they wait 4 yrs to make this claim? And the agreement they keep referring to became void the day the other tenant moved out.