All, thank you for your help.
Three thrusts I have picked up:
1) let the holiday continue.
2) this behaviour cannot go unconfronted
3) at nearly 14, waiting for a few days will not harm him, and may even add value. I have therefore decided that there needs to be a conversation when we return home: depending on the direction of that conversation, I might punish him. But I will not pre-judge.
Henry
When my children misbehaved on holiday I would spank them that night when we got back to wherever we were staying. The only time I have delayed a spanking was on Christmas Day, when I spanked my son the following day. One may argue it could have spoiled his Christmas knowing he would be spanked the next day, but I spanking him would have spoiled everyone else's Christmas.
I’m pretty sure I’ve never shared this before, but the first Christmas after mom adopted me, a Cousin and me earned a spanking first thing Christmas morning. Our Moms just took us to the next room and took care of business. It greatly impact my enjoyment of the morning but I was still able to enjoy later in the day, I don’t think it greatly impacted anybody else, And meanwhile I can imagine waiting till the next day and having that hanging over our heads when we were supposed to be having fun
Last night we stopped overnight in Christchurch. My youngest has arranged to go out for the day on Thursday with school chum and parents.
Matthew immediately asked if we could postpone the conversation until Thursday when Mark is out. I agreed.
The subliminal message from this is that Matthew thinks that a sanction is coming and wants to avoid the embarrassment factor.
Let's see what Thursday brings.
Henry
Samantha always has a brush in her purse "just in case"
I always waited until we got home even if we were camping.
Mark has left: Matthew and I will be having our chat in half an hour or so. At this stage I'm more interested in identifying the issue (s) and preventing recurrence than I am in paddling him; though that remains a possible outcome.
I will have the chat on neutral ground, not his bedroom (where discipline conversations often happen) or the garden room (where paddling happens). If it just feels like 'prelude to paddling' he won't open up, his mind concentrating on the sore bum to come.
H
I will be updating this on the thread "kitchen table" shortly.
Thank you all for the advice; I hope I have converted it to wise action.