Trickster Andy Todd, 47, from Dawlish, Devon, was giving a speech when he was filmed picking up the cake to thank its maker.
But screams of horror were then heard among the guests as the video captured the moment the heavily-layered sweet treat, which was really a fake, went tumbling to the floor.
Newlyweds Dina, 23, and Johnny Smart, 24, didn't know what to do and looked on in total shock following the unfortunate slip.
But Andy, a caterer, then revealed the whole thing was just an elaborate prank.
In the footage Andy is heard saying as he picks up the cake: 'I'd just like to say - has anyone looked at this cake, because it is absolutely fantastic.'
His daughter Dina can be heard saying in the background: 'Don't lift it dad.'
Andy then drops the cake before quickly reassuring the worried crowd by saying: 'Don't worry - it's all right, it's OK - because the real one is at the back there!'
'I made sure it only lasted a few seconds before I pointed out the real cake at the back.'