Broomstick: Your information is completely incorrect.
Concorde can and does hold, just like any other aircraft. There are no type-specific restrictions on normal manoeuvring procedures, and holding is handled just like any other type. It is unusual to have less than 20 minutes fuel holding capability inbound LHR from JFK, and much more can be carried if the situation warrants it. It might be an idea to check your facts before making inappropriate comments like <<some slight of hand to accomodate another straight in wonder>>.
Hope this helps.