Anne Dicks has sent me this link to an interview with Boris Johnson that her daughter videoed and edited. Anne tells me:
He had been up all the night before with the local elections, and this recording was made by Jenny with my camcorder at 5pm during a massive day at the University of Bath Spa. I think it speaks volumes for Boris's desire to help promote Classics that he managed to organise his ideas and sound so coherent under these circumstances.