I used to work in cheque clearing, debit outwork. An employee (not me!) lost a bundle down the back of a piece of furniture and there they laid for more than six months, we cleared them.

Actually, Donald Duck could sign them and they'd probably still clear you know LOL.

I'm guessing though that the account that the cheque was written from is now closed though ? When the new company aquired the old one then they should have had accounts showing what cheques written/amount owing etc before closing the account.