This was originally a 1965 Italian song, Lo Che Non Vivo (Senza Te), by Pino Donaggio and Vito Pallavicini. The English lyrics, which have nothing to do with the original, were written by Simon Napier-Bell, manager of the Yardbirds, and Vicki Wickham, producer of the TV show Ready Steady Go!
Released on March 25, 1966, it was Springfield’s most successful single, topping the UK charts and reaching No 4 in the US.
Here is a live performance.