It is almost impossible for a professionally made croquembouche to collapse – indeed they can be far more stable than a traditional cake. It must, however, be correctly handled, and this includes displaying it on an level table, and keeping it dry. It should not be refridgerated, and special care must be taken for marquee weddings as marquees can be very humid. I would usually advise having the cake cutting ceremony as soon as you come into the marquee or reception room, so that the photos show it looking at its very best. This also gives the caterers plenty of time to break it up before serving.