There is a time-line with some info on the autoexpress (a UK motoring magazine) website [here] (http://www.autoexpress.co.uk/car-news/driving-test/85429/history-driving-test)

It states that during WWII examiners were were redeployed to traffic duties and supervising fuel rationing.

And during the Suez crises they were again redeployed to supervising fuel rationing. This info is also published on the UK government's website

https://www.gov.uk/government/publications/history-of-road-safety-and-the-driving-test/history-of-road-safety-the-highway-code-and-the-driving-test

Can you link to the article so we can see if they cited any sources?