[Neil Jones]

Didn't Des Lynham have form for sometines being a Dictionary Corner guest when Richard Whiteley was still alive?

Was Des O'Connor ever on the show (i.e. in Dictionary Corner) before becoming its host?

Apparently Des Lynam was only ever in dictionary corner once, and that was in 2010:.
wiki.apterous.org 

The same website suggests O'Connor has never been in Dictionary Corner either.

While we're here, neither has Nick Hewer, Jeff Stelling or Richard Whitely (or Carol for that matter, both for obvious reasons). Anne Robinson has (last seen in the late 1980s as a guest) and Colin Murray has as well.