Don't understand the thinking on blocking car park roofs, etc. for security on an event like this. If there are a few hundred enthusiasts at any particular point how would some terrorist pull their SAM out of whatever holdall, lift to shoulder, acquire and fire without anyone - let alone the plod - seeing them. These things aren't small.
If they want to do a suicide bomb explosion why choose a roof not inside the terminal.
Daft, really!