This might need a little more explanation in 2013. In the mid-seventies, there were still only three TV channels and very few programmes, even given this limited choice, during the day. For long periods there was nothing on the screen but trade test transmissions, largely there to enable TV shops to get the best possible picture on their display sets. These transmissions were made up of the testcard, with its instrumental soundtrack, and the occasional test film - like The Home Made Car, a 1963 Academy Award-nominated short which was shown no less than 182 times between 1962 and 1973. During the school holidays, or on Saturday mornings before your parents were up, there was little else for bored kids to do but watch the testcard and transmitter information - the music and the images became as embedded in the minds of a generation as The Monkees and the Robinson Crusoe theme.
The most iconic image, introduced in 1967 with the advent of colour TV, was called Test Card F. Its designer was a BBC engineer called George Hersee and, for a dummy run, he had included a picture of his eight year old daughter, Carole, at the centre of it. The BBC decided that replacing Carole's picture with an adult model was too risky - they needed something timeless, and 1967 fashions weren't exactly built to last. So Carole went into a photographer's studio: the result was the familiar image of a girl with an Alice band, playing noughts and crosses with a rather terrifying toy clown, surrounded by mysterious test graphics. Miss Hersee was unsurprisingly teased at school and, to her discomfort, the image was used on a daily basis until 1998. Now living in the New Forest with two daughters, she can claim to have had more screen time - around 70,000 hours - than anyone else in British TV history.
As a child the image seemed incredibly important. For girls, the Mona Lisa-like image of Carole Hersee was a role model - I know a DJ in Wales who dressed like her as a child, even carrying a cuddly clown around; someone else I know thought she was the most beautiful girl in the world (no, it wasn't me). Later on in life, the image of Carole Hersee became more associated with waking up on the settee at three in the morning with the telly still on and empty beer cans on the floor. Her face never changed; the game of noughts and crosses never ended. It was once compared to a Home Counties version of The Seventh Seal.
But it was the testcard music that hooked me. The BBC regularly received letters from the public asking where they could buy the music; the short answer was, they couldn't. The man tasked with choosing the testcard music in the seventies was John Ross-Barnard, who worked in the BBC's Foreign Recordings Department: "People wrote in - can I have a copy? But it wasn't ours. It came from music libraries, and a huge exchange of material between European broadcasters. The public would receive a photocopied letter saying the music wasn't for sale. It was an embarrassment, in a way."