Most Out of Date BW Licence Still on Display?

Lots of boats on the system don't display licences. Lots of boats on the system display licences that our out of date by some months. A few display licences that are a few years out of date, but recently I discovered a boat displaying a licence that must be some sort of a record.

Just north of Braunston on the North Oxford we passed a dilapidated, but floating, GRP cabin cruiser displaying a 1997 BW Licence. Is this a record for the oldest licence still on display? Sorry I cannot provide photographic evidence, it was difficult manouvering past the boat since it was moored close to a partially collapsed bridge.