The Royal Marines at Lympstone were hosting several members of the Guards Regiment. During breakfast one morning, a Guards officer entered the Mess wearing his cap and sat down. 

The Royals were bemused but remained silent. 

 During the course of breakfast, one of the Royals turned to the offending Guards officer and asked him to pass the salt. No reaction. He asked again. Still no response.

At this point, a fellow Guards officer informed our Royal that it was traditional in the Guards Regiment, that when an officer did not want to be disturbed during a meal, he wore his cap to the table.

The Royal absorbed this. Thought. Then, he got up and placed his size 9 combat boot in the Guards officer's bowl of cereal, saying:

"It's traditional in the Royal Marines, that when a Royal sticks his boot into your cereal, it means 'can you please pass the salt'!"