Work at the station has recently uncovered these amazing advertising posters in non-public areas and that date from c1956 - 1959 when the station's lifts were removed and replaced by escalators. These are in an old lift passageway and will be safe.
This is a poster advertising the still popular Ideal Home Exhibition, sponsored by the Daily Mail, that was held at Olympia in March of that year.
We will be leaving these intact - and please do not pester the station staff as the posters are wholly inaccessible - which is why they've probably survived 50 odd years!
The photos were taken officially - please do credit London Underground in any links.