will the dodgy shop owners who deliberately sell drink to underage customers not just write another shops name on the bottle?

Nice one, a very simple but clever idea; I hope that maybe one day they will come-up with a more secure idea such as an invisible ink stamp to cut-back fraud on the bottles.

Where cn I get a pen. I need to mark my bottles in my drinks cabinet case my tenage sons knick them,LOL.

i think now its time for id cards ...no card no drink...but would it not have been better marking the said items in the factory so even the shopkeppers dont no where they are.....after all your local corner shop are the biggest crooks of them all...if they can make an extra penny from us they will so they can send it home abroad...so we can have more corner shops when they come over..