My understanding is that once a Speaker retires he is barred for life from returning to partisan politics, as per the following quote from the parliament website
"Speakers must be politically impartial. Therefore, on election the new Speaker must resign from their political party and remain separate from political issues even in retirement. However, the Speaker will deal with their constituents' problems like a normal MP."
The important phrase being "even in retirement"
However the current speaker, John Bercow, is now being suggested as a potential leader of an interim government to replace Boris Johnsons Conservative government after a vote of no confidence.
My question is not about whether or not this is a good idea, but simply "is this even possible?"