"You've got to know who Manuel II Paleologus was," Mr Johnson said. "Hardly anybody in this country could remember who he was, let alone pronounce it.
Yet he causes a huge row, 700 years later. It's crazy to ignore the power of these subjects."
Mr Johnson spoke to The TES before he launched a classics programme at Cheney school, a comprehensive in central Oxford. The promotion of classics in state schools is led by Lorna Robinson, 27, who this year quit a teaching job at Wellington college, Berkshire, to take classics to the masses.
Eton-educated Mr Johnson said state schools were discouraging pupils from taking Latin and Greek: the subjects were harder, and schools were under pressure to perform well.
So the classics were being "ghettoised"-albeit in the rather green and pleasant ghettos of the independent and grammar schools.
"Universities have got a problem because every time they admit someone to study classics or Latin or Greek, on balance they are probably going to be admitting someone who's already had a pretty privileged education," said Mr Johnson, adding that "tragic" comments by Charles Clarke, the former education secretary, criticising non-vocational subjects such as classics, typified the Government's attitude. "They see all education as being entirely utilitarian, and about inputs and outputs and generating tax revenue," he said. "So you boost certain subjects that you think will boost the economy, like science or technology or law. And you forget the huge potential of the classics to enrich people."