From the Historic England blog, a Brief Introduction to England’s Secret Printing Presses.
“Banging Out” was a way of newspaper printers commemorating something special: a long-serving employee retiring or even the closure of the presses. This short film, via. Typoretum, explains the tradition. Source: Banging Out – Fleet Street Remembered. – A Blog about Typography, Letterpress and Printing History | News from Typoretum