Thank you to all those who entered, especially everyone who taped money to their postcards. There was no outright winner, but a special mention for Len Filth from Scunthorpe, UK, who was nearly right with his suggestion that Jarvis might respond by dressing up as Secretary of State for Environment, Food and Rural Affairs (I'll bear that crazy outfit in mind for the next book!)
Particular commiserations must go to Poultice Ungawa of Croydon, Brazil, who took it upon herself to leave her entry in a Tesco bag for life on my doorstep at dawn. This really demonstrates the efficacy of the blog in inspiring such fervour in its followers, and don't worry Poultice, I've alerted the authorities who now have your description. Your entry has been safely defused, and we've been allowed back indoors after the evacuation. Better luck next time.