CANADA in the 1950s. We are in the apartment of petty civil servant

Henry Benedict Stuart, where his wife Lilian puts on airs, boasts of her

family connections and lovingly dusts the reproduction Annigoni portrait

of our dear young Queen. Elderly eccentric great aunt Clementina

announces her latest success in patent medicine testimonials -- she has

become the Flush of Youth Lady in an advert for laxatives.

Home comes handsome Mr Stuart, a mild, pleasant and unassuming

middle-aged man, just in time to meet two visiting scientists from a

research foundation studying heredity, one of whom is the extravagantly

dressed and thickly accented Dr Maria Clementina Sobieska.

Get that name? No wonder Doc Sobieska drops on her knees and hails

Henry as ''Majesty''. Plain Mr Stuart is none other than the last male

descendant of the Young Pretender.

The plot thickens. Nestling in Dr Sobieska's bosom is Bonnie Prince

Charlie's snuff box, now containing an anaesthetic powder which will

regress Mr Stuart to his ancestor's melancholy years in exile. He sniffs

and lo, quiet Henry is transformed into the autocratic princeling, with

devastating consequences for the household.

Well, there are some funny lines. Victoria Hardcastle brings silly Mrs

Stuart brilliantly to life. Stephen Finlay nicely contrasts pale Henry

and outrageous Prince Charles. Ann Scott-Jones goes gorgeously over the

top as Dr Sobieska.

The play, by the Canadian writer Robertson Davies, has never before

been staged in Britain, which is not our loss. It may serve to while

away an idle hour or two on holiday in Perthshire, which must be the

sole justification for its inclusion in the Pitlochry season.