To John MacKenzie.The picture with the three guys from the 70s.Paddy Moloney and Sean Keane of The Chieftains(as you said).The suited one is Garech Browne.We're really talking posh here!.His father was a lord and his mother a Guinness heiress.He became a patron of Irish folk and traditional music,even started up a record label.
On a sad note, his younger brother,Tara, was killed in a motor accident in the West End when he was 21.This is commerated in John Lennon's song 'A Day in the Life'
You'll find more about him on Wikipedia.