Can Scottish Power make me pay a BACKDATED Electricity bill from 2013!!

Other

Hi All

Out of the blue I have received letters from ACI a debt collection agency chasing me for historical electricity debts on behalf of Scottish Power at 2 Flats in a property that I sold in 2019. 

In their letter ACI threaten Solicitors and CCJ to recover the debt.

When I engaged with ACI about the £460 bill for one of the flats from 2017 - 2019 they said I was also due for a bill for the other flat going back to 2013 as well !

Is there a statute of limitations to prevent energy companies dredging up bills from the past please and if so how does this statute also apply to Landlords who own property in their own name (i.e. not through a Ltd company) and how far back are they allowed to go (years) in chasing a bill?

It took me absolutely ages to find evidence that the first of the 2 flats was empty and boarded up between 2017-2019 (council tax bills from archived accounts). But going back to 2013 ! Really?!  I have no chance of finding stuff from that far back - probably destroyed. 

I wonder therefore were Scottish Power within their rights in chasing me for a bill from 2017-2019?

Are Scottish Power also within their rights for chasing me for a bill even further back in 2013?

Going forward, how should I now deal with ACI and Scottish Power on this matter?

Your kind input would be gratefully appreciated.