If you've read Worldshaker, you'll know that, when the revolution happens at the end, the Filthies plan to change the juggernaut's name. Riff likes the sound of 'Liberator' and, yes, that's they name they choose - so the sequel is called Liberator.

How much to give away? I'm a blabbermouth, so I'll blab - in the second book, the Filthies revolution moves into a new phase, more violent and extreme. Col and other Upper Decks people who have stayed to help on the juggernaut are viewed with suspicion and hostility. It's partly because of the mysterious acts of sabotage that keep happening. In the Revolutionary Council, moderate voices are drowned out and extremists take over.

I'd better shut up before I start revealing who the saboteur really is! I'll just say that most of the characters from Worldshaker reappear inLiberator: not only Col and Riff, of course, but Gillabeth, baby Antrobus, Quinnea, Orris, Septimus, Professor Twillip, Mr Gibber … they're all back, as weird and wonderful as ever.