Complex sentence: The single returned to the UK top ten a year later when used as the theme music for the BBC documentary series Sailor about "HMS Ark Royal", and having been a hit twice over became, Stewart's biggest-selling single in the UK.
Split into simpler sentences: The single returned to the UK top ten a year later when used as the theme music for the BBC documentary series "Sailor", about the "HMS Ark Royal". Having been a hit twice, it became Stewart's biggest-selling single in the UK.