Happy birthday to John. I was the Dubliners's road manager in 1967 and penned a couple of songs for them including Seven Deadly Sins.
I wrote the sleeve notes for their Live at the Albert Hall LP, individual sketches and this was on John:

Beneath John Sheahan's bushy chin,
He hides a flute and mandolin!
But when our John is asked to play,
His fiddle's never far away
And play! the man will play you any
From Zozzimus to Paganini.
No gargle ever wets his lips
(Except unalcoholic sips).
Though up and down OUR elbows go
When John's goes up, the tunes will flow!
With solemn face and twinkling eyes,
His long bow-sweeps draw praising cries:
A touch of tear-jerking vibrato
And a final, cheeky "pizzicato"!