Sounds like a shrewd move. You can be too successful in bringing numbers in. Also allows a vetting of those attending to keep the potential trouble makers out before they arrive. Mike is quite able to turf them off his land but simpler if they are not present in the first place.
I am not so sure this is not going to be a more common part of organising events now. Unless your tooled up to do a National or something, where numbers can be catered for and the emphasis seems slightly different, predicted and groomed numbers just make for a much simpler life then catering for those attaching themselves to something having not understood quite what it is all about and who then create issues when things do not suit them or simply choose to confront a consensus of activity.
Messerschmitt set, Goggo Dart, Heinkel 175, Fiat Jolly, Autobianchi Cabrio
MG ZB Varitone, Wolseley 4/44, Borgward, Saab 96s, Bellamy, Isuzu Trooper, Citroen BX 17TZD pair, GTI 16v
Selling - Vellam Isetta, Bamby, AC Type 70, Velorex, Church Pod 1, Reliant Mk5, KR200, BX 14 E, 16 TRS Auto, 19 TXD Es