Most of the time jets like that are chartered - far cheaper and more practical than having your own one.
There are a lot of companies like this one out there.http://www.premieraviation.com/index.htm
Apart from the convenience, the costs aren't hugely inflated compared with booking last minute seats for a team of people with plenty of leg room - especially when it counts as a business expense.
thanks Sparkle. I'd assumed he'd hired it and hadn't really thought that it might not be that uneconomical in the circs. I associate private jets with the likes of smugfed. Anyway nice that he could give JW and his team a ride. And of course it might have been difficult to get from Madrid to Rome at short notice on a saturday morning so agree it makes sense (though not very green).