London - Mental slippage and cognitive retardation have wreaked havoc on HM's sunset years after decades Commonwealth ganja dependence a royal source said today.
Palace quacks' insistence on bleeding her with leeches first identified the scale of the problem after medicinal maggots began mutating.
Whole colonies of 'spent' leeches were then harvested for analysis of digestive secretions.
And the suspected mood adulterants siphoned off for Palace staff recreational use.
"Now you know why several Caribbean islands as known as Commonwealth Dependencies, heheh," royal proctologist Professor Sir Einstein Flintstone said today.
"She's got whole plantations of the stuff - including domestic F1 hybrids growing in a converted Buckingham Palace composting lav."
Tomorrow evening the Queen is rumored to appear 'in a puff of smoke' at the Paralympics Opening Ceremony in a move calculated to upstage Danny Boyle.
She'll then be airlifted back to her Balmoral hydroponics suite for the usual weekly seance about constitutional advice.
Prince Philip's chillum is being refurbished in time for the Camerons' annual visit.
Daft sod is likely to croak it around Friday's full moon.