As the title says, I am a plonker. Just realised that I forgot to put my tachograph on break for the 12hour crossing to Rotterdam and I can’t get to the lorry to change it. Oh well at least I’m only loading in the docks when I get there and returning on tomorrows boat so I can stick it on break when I get off in the morning. 
You could always do a manual entry and don’t forget to keep your tickets especially if you do a ferry movement to back it up, should you get stopped within the next 28 days