I wonder if they'd notice a large bottle of marmite with a detonator in it - a mobile phone battery would set off the detonator with no trouble.

I know somebody who caused a panic because they had two large slabs of marzipan in their bag.

When they x-rayed my guitar case, they got upset about: my curly guitar lead, the internal pickup lead which looked like a big fishook, and the electronic tuner.