Please see cover illustrated below:


The cover was posted in Abidjan, Ivory Coast, on 6 March 1956.
It appears to have been opened at the right, resealed with a plain white strip of paper and stamped with a two-line handstamp 'ABIDJAN' and a further two illegible words.
There is a manuscript annotion "Vu au controle", and initials or a signature.
My question is for what purpose would mail from Ivory Coast to Great Britain be opened and inspected in 1956?