The problem is that the British public are essentially stupid and if someone tells them there is a shortage, a small but significant percentage will buy cucumbers even though they don’t need them.
I'm old enough to remember the great sugar and potatoes shortages. Both were (Perhaps deliberately.) caused back in the 1970s by a newspaper publishing a story that sugar would be in short supply, the ensuing panic buying ensured there was indeed a shortage with stores rationing customers buying multiple bags of sugar. Other news induced 'shortages' were generated later in the decade of salt, potatoes and sugar again.
There was a grain (Pun intended, sorry!) of truth to each shortage, the potato one being blamed on the Long hot and dry summer of 1976, but the reporting of each issue exacerbated the shortage by triggering panic buying.
There was a bread shortage too, but that was due to bakers' striking asking for a 60% wage claim following rampant inflation. Ring any bells here? It makes the nurses' and railwaymen's claims look tame doesn't it.