I Remember the Test Card

When tellies were still young in the UK there was a test card. I remember it so well, as much as I remember my fave TV shows. Trouble is, I don't know why I know the test card because it only appeared at midnight or thereabouts. The end of telly. The cut-off point until the morrow. Was I up at midnight or did the test card go right into my teens and beyond in the Seventies? I recall my old Dad…