Political misfortunes rarely come in isolation. If anything, they prefer to breed. That's certainly how it feels watching the Coalition Government fall so spectacularly into its slough of despond. It's not even as if anybody else tripped them up. Every element of the present malaise has been a home-grown Jack and Jill-style tumble. The NHS Bill, the petrol panic, the botched Budget, Theresa's May Day (in April). These were all unforced errors.