Short burst of bubbles every 4 seconds or so. The first sign of fermentation (in the airlock anyway) came around midnight when things started moving, by 08:00 the first white foam was visible. Two hours later and the foam has dark brown edges (I’ve not opened the fermenter – just looking through the semi-opaque sides) and is just touching the top of the lid. I’m going out for a couple of hours now and fully expect there to be a mess when I get back.