TANNOY: Conversations about Tannoy Lancasters

I've just collected my pair of Tannoy Lancasters, which are in good cosmetic order but I'd like to take the grille off to examine the drivers' cones. There does not seem to be an obvious way of removing the grilles, so maybe they are not removable as such? Can anyone enlighten me on this and save me from causing inadvertent damage? Many thanks. Pics will follow when I have time.