After finally pitching the yeast on Sunday at 20:30, and witnessing the first "galump" of the primary fermentation two hours later, I was dismayed to find the next morning that there were no "galumps" and all activity had appeared to have stopped.
Only later in the day did I notice that a thick, creamy surface (the "krausen") had started to form on the surface of the wort. But, it wasn't until around 22:30 (pitch + 26 hours) that I could detect the pressure of the carbon dioxide pushing the airlock level towards a bubble.
This morning, I'm glad to say the "galumping" is regular, although far from frenetic, and I now have a full 3-inch (8cm) krausen on top of my beer - a new record for me.
Let's hope it continues.