On past events, the first 'hundred' classics to arrive were allowed infield. Check the event website, but if that's the deal, you'll need to be there early...... Like before 0800 I imagine.
Checked but nothin' doin' on the first 100 classics. My experience of the gate staff at Silverstone is that they are totally "by the book" - no pass, no entry. I have a call out to the organisers and will post here if successful in case any other Morganisti on here are planning to be there.