Actuarially, it is very plausible that he [Prince Charles] will predecease his mother, whose constitution seems more robust than Britain’s.The Office for National Statistics (ONS) provides data on life expectancy in the form of life tables. Within these, ONS proposes that the “Cohort expectation of life, 1981-2058” is the “more appropriate measure of how long a person of a given age would be expected to live, on average, than period life expectancy.” Various projections are available, but the “Principal projection” provides a life expectancy for a UK female of 85 of 7.5 years, and for males of 62 and 63 life expectancies of 20.9 and 20.1 years respectively*.
While it is impossible to proceed from the general to the particular, and also there will presumably be some inheritance of longevity, mother to son, actuarial plausibility would seem to suggest that good King Charles III's golden days** will last more than a decade!
Engel might have been influenced by Princess Diana’s prediction that Prince Charles would never be King and that William would succeed his grandmother.
*Queen Elizabeth II (85) was born on 21 April 1926, and Prince Charles (62) on 14 Nov 1948.
**Song: The Vicar of Bray
In good King Charles's golden days,
When loyalty no harm meant;
A furious High-Church man I was,
And so I gain'd preferment.
Unto my flock I daily preach'd,
Kings are by God appointed,
And damn'd are those who dare resist,
Or touch the Lord's anointed.
And this is law, I will maintain
Unto my dying day, sir,
That whatsoever king shall reign,
I will be Vicar of Bray, sir!