The Madness of George III, Chichester Festival Theatre, until Saturday, November19.

Haig’s George III in Alan Bennett’s superlative play starts off affable, inquisitive and intelligent, jumping into bed beside his Queen as he cosily declares the happiness of “Mr and Mrs King.”

His descent into insanity is shocking to behold, no holds barred as Haig shows him become a wretched, babbling wreck, lewd, incapable of shutting up and knowing no boundaries in an agony worsened at every turn by the incapable physicians sent to cure him - until Clive Francis’ Dr Willis turns up.

On the sparsest of sets, Haig shatteringly lays bare the fall of a decent man, while around him politicians and family jostle for power in a world in which they simply cannot see him ever being cured.

And yet he does come back - and most movingly so, director Christopher Luscombe orchestrating everything to perfection in a truly great night at the theatre, one laced with wit amid the pain but above all full of compassion and the sheer power of the human spirit.

By Phil Hewitt