Bet he has a particularly pleasing Baritone.
As for the ex PMs, I'd say
Sunak - treble
May - 'I'm a soprano really, but I like to help out the Altos from time to time'
Cameron - respectable tenor
Brown - Bass
Blair - Tenor with a Dylan nasal edge whenever somebody had a guitar in the vicinity
Johnson - Shane McGowan Sings Gilbert & Sullivan
Major - Tenor that struggles on the high G and above
Thatcher - 'I'd never do something as frivolous as sing, not when I've got the Poor and the Miners to stamp on'.
Allowed herself a few bars of Evita after entertaining Pinochet, though.
Truss - How dare you ask if I can sing?Everybody knows I should have played Mary in the school Nativity with my solo version of Little Donkey. But they gave my part away to somebody called something stupid like Jessica who had red hair. I told them THAT IS UNACCEPTABLE, but they laughed and handed me the Donkey ears anyway. I was cheated out of my role by that conspiracy between Jessica's mum, Mrs Chumley the Head and Freddie Twatterson's dad who was the caretaker.