The condition presents problems that are as much metaphysical as medical. If porphyria is a metabolic disease, the symptoms of which are similar to, and which even today can be mistaken for, those of mental illness, in what sense is a sufferer from porphyria different from someone who is more routinely deranged? In what sense is all mental illness physical in origin? These are large questions and I didn’t want to venture into what is both a swamp and a battlefield, but felt that I needed at least to show that I was aware of the problem. Hence this exchange between Greville and Dr Willis:

GREVILLE  Do you think His Majesty is mad? Sometimes he seems … just … ill.

[The dots indicating my opacities as much as Greville’s.]

WILLIS  Perhaps. But he has all the symptoms of madness.

GREVILLE  So what is the difference?

WILLIS  I am a doctor, Mr Greville, not a philosopher.

‘And this is a film,’ he might have added. ‘And I’ve not been got up in a bob wig and black silk stockings just to safeguard the intellectual credentials of the author.’ So the exchange was, of course, cut.

There had to be some sort of explanation, though, if only because of the scenes involving the urine. But since it was only identified in the 1930s, porphyria could not be acknowledged in the film or the play without anachronism. When the play was first put on at the Royal National Theatre, there was a penultimate scene which catapulted the pages and equerries into the twentieth century, where Mrs Macalpine explained about the blue piss. This didn’t entirely work and when the play was revived the following season, the scene was omitted. Trying to work out how to get across this information in the film, I sometimes wished I’d been writing for Hollywood thirty years ago, because then there would have been no problem:

EXT. RIVER BANK. DAY.

As Braun and Papandiek pour the contents of their chamber pots into the river a sudden shaft of sunlight catches Papandiek’s face and he looks up, dreamily.

PAPANDIEK  There will one day come a time when our master’s disease will be recognized for what it is … not madness – (Cue Heavenly Choir.) – but porphyria!
He raises the crystal chamber pot to heaven and we see looking down on him the faces of Mary Queen of Scots, James I, Queen Anne, George IV and Frederick the Great. And they are all smiling!

Except, of course, that they wouldn’t be smiling, because even though the condition is more often (though not always) diagnosed today, there is still no cure, just improved alleviation.

Monarchy is a performance, and part of the King’s illness consists in his growing inability to sustain that performance. When the King is on the road to recovery, Chancellor Thurlow discovers him reading King Lear and congratulates him on seeming more himself.