No problem when it comes to quietly practising zentangle, you would say. However, apparently my head was a bit distracted, because when I had almost finished my tile, I realised I had been using H (Hibred) and two times Y (Yoga and Yew-dee) - and no A!!
Luckily the tile wasn't fully finished: I managed to put Arabel in the bottom left corner. Phew, just in time :-)