At a ministerial level you would at least expect someone to do a bit of homework especially in an area for which they are key in shaping. I think is bordering on the facetious (barring tiresome devils advocacy I suppose)to insiste that a minister should not know anything at all about their brief. So my money would be on a Transport minister who can drive, no not strip an engine down, but know the rudiments of a common vehicle such as a car. If a minister for transport were to say..'When I think of the word ignition and clutch..well I just go bzzzz' Would that REALLY inspire confidence in you as a member of the public in such a public official?