We had to name the horse because obviously it wasn't named for racing, so we had a chat with Simon. His first suggestion was 'I think we should call him Simon'.
They eventually settled on the name It's A Yes From Me - a reference to a phrase often used by panellists on Cowell's talent shows.
Ant McPartlin added: "It hopefully might run in the Summer."
And and Dec previously owned another horse which they recently sold.
They also told Ross they have had to insure themselves as a double act, so the other would get a payout if their partnership was jeopardised.
Donnelly said: "Financially the other one would get a kick back off that. Every cloud - we have insured each other against that."
McPartlin went on: "The problem with that is that if one of us has a fatal accident, we're the first one that the police will come to because we've got a motive."
The pair famously had a chart career under guise of PJ and Duncan, a spin-off from their roles in BBC series Byker Grove. But McPartlin admitted their music did not really stand the test of time.
He said of their songs: "I can't even name them. They're all pretty bad."