The young pretender, who recently signed an EMI recording deal for pounds 1.1m, double the amount Seamus Heaney received for the Nobel prize for literature, performed to a packed room of 30 people on the fringe of the festival. Horovitz junior was there, cheering through the lyrics to "Everyone's Taking Cocaine", and whooping it up to a 30-second number on the trials and tribulations of being a supermodel.
At the end of the performance, Adam could contain himself no longer. "Murray Lachlan Young," he barked, "has done more for poetry in the last five months than my father has done in the last five years." Relations, it seems, are strained.
Horovitz jnr, who will be performing poems from his recent anthology, Hoo-Hah poets, just doesn't know what his father's problem is. "At least Murray is turning people on to poetry." And will Horovitz snr be coming down to Cheltenham to add support to Adam's Hoo-Hah extravaganza?
"Umm, no, he's kind of busy."