That's the one I had in mind.
After being a Whig/Liberal stronghold for centuries, things got a bit more interesting in the 20th century, with the Liberals, Labour, Conservatives and Plaid Cymru each holding the seat at least once.
I have to admit a
mea cupla, in that I've just found that there has been
one instance of an incumbent being voted out by the people on Anglesey in the past century: 1951 saw Liberal MP Megan Lloyd George lose her seat to Labour's Cledwyn Hughes. With that one exception, the people of Anglesey have proved themselves to be very faithful to whoever they've elected in the past, and only changed their allegiance when the incumbent has chosen not to stand.
(The current MP, Albert Owen, has chosen to stand down at this election, so that trend is destined to continue for at least another Parliamentary session.)
With apologies for the minor slip-up, the polling booth is yours,
martinsh...