It's because I'm writing elsewhere.
I've been re-working the Oliver Drummond and the Four Horsemen story - including new elements which come pretty much right in at the beginning: more suspicion and (hopefully) more tension. They're going well and I'm liking the new inclusions. I think it'll make the story stronger and let the reader ask more questions about some of the character's motives.
I've also (in the last couple of days) starting fleshing out the plot for the (as yet unnamed) Tiberius Found sequel - oooh, there's some stuff going on: revenge, betrayal, intrigue, power-gaming, double-crossing. I'm thinking it'll be a touch darker and harder than Tiberius Found - the Daniel Henstock at the end of the story isn't the same person from when it started, and those events have changed him. His world's different and he comes to realise that the stakes are now much higher.
At least, that's how the Beat Sheet is shaping up. Right, back to it ...