The Madness of King George, Nat Theatre Live (YouTube) until June 18.
Mark Gatiss swivels effortlessly between a swaggering and a gibbering monarch in Alan Bennett's play, a joint production between Nottingham Playhouse and the National Theatre.
The story of the18th century king is rooted in truth but was made so much more palatable after it was re-imagined by Bennett in 1991. Regular stage productions and a film followed.
Some lines are simply unforgettable - like the "eloquence of a stool" as doctors ignore the king's unusual urine colour and instead purge, boil, bleed and provide enemas in a bid to get to the bottom of his malaise.
Mark Gatiss is truly in command of the stage which is itself a model of engineering elegance.
His scenes with the queen (Debra Gillett) as they settle down to bed - fondly calling each other Mr and Mrs King - raise a smile before the shattering disturbance of the royal synapses and the mental descent into the hands of a quartet of quarrelling doctors, some of whom are definitely on the side of the prince in waiting.
Is it Britain's loss of America - as Pitt the Younger (Nicholas Bishop) may fear as he clings on to power in Parliament? Later studies indicate it was more likely a physical complaint that poisoned the king's mind.
I loved the little vignettes - like how one of the footmen grew so tired of the situation that he resigned his position at the palace and opened an upmarket London grocery store.
His name? Fortnum, of course.
The National Theatre has announced the following productions will follow on YouTube: Small Island, A Midsummer Night's Dream, Les Blancs, The Deep Blue Sea, and Amadeus. They will all be streamed for free, although the NT asks for donations. Full details of dates and times on our News page.