The Guardian has reported that Boris Johnson wants to secure control of the courts and the prosecution service, a move which would put London’s mayor in charge of the criminal justice system in the capital. It has said that
The plan would see control wrested from Whitehall and the devolution of the most important pillars of the justice system.
I find this suggestion quite extraordinary. One of the most basic functions of the state is to deliver consistent, fair and accountable justice across the country for which it is responsible. Devolving this power would be to undermine the state itself (whilst the recognition that Scotland has always had a separate legal system is, perhaps, the strongest indication of its separate statehood).
London is not a state. If it were to be a state within a state then it would be very prone to capture by the other existing state within a state in the UK at present - the City of London - and that could lead to all sorts of abuse.
Devolving tax powers from the state might be macro-economically unwise. Devolving justice itself would be to signal the end of the state, in my opinion.
Is that what Johnson wants? It may be, of course. In that case, worry.