A lack of principals

What is the collective noun of Prime Ministers asked James Callaghan to which Harold Macmillan instantly replied: a lack of principals.

England (Yukay if you must) had 6 PMs in the 1760s and 8 from 1827 to 1837, not counting Wellington twice. 

PMs were gentlemen then and read Homer. 

We will have had 7 when the new man takes office since 2016, of whom only one Johnson could read Homer and only one Cameron was a gentleman. 

Or can he read Homer too? Possibly but I doubt it. 

All the recent ones have been terrible. Compare Grey, Peel, Melbourne or Canning. To say nothing of Wellington who wasn't a very good PM but was much better than Starmer.