It was to the tune of 'My Bonny Bairn-i-o' (Oh, the shearing's not for me my bonny bairn-i-o etc.) I remember Ian Walker did it in the 80's but I don't know if he wrote it or if he still does it now:-(

The phrase, if memory serves me well, is 'My life's greatest thrill'.

Hope this helps

Dave the Gnome