That reminds me of the late 1970s as a student in Birmingham. I had a Mini with a Pioneer cassette deck but no radio. My mate had an Austin 1300 with a radio but no cassette. He used to love coming to Swansea with me for the odd weekend (and Plastic Sam down at the Langland Bay hotel on a Sunday night). If it was my turn to drive, as we approached the tunnel at Newport he would reach across and turn the sound off as we passed through as it used to irritate him that when he drove, his radio would cut out while we were in the tunnel.