The Patrons Lunch is a massive publicity stunt, attended by carefully selected people from charities closely linked to the royal family. Peter Philips, as you say, is not doing it, er, for charity. It costs £150 a head to attend for the 10000 attendees. If you haven't got a ticket you won't be able to walk along a street that is normally open to you. It's all about the left hand definitely knowing exactly what the right hand doeth.