In which year, was this English rock band formed in Hertford that the lead vocalist Ian Gillan of Sabbath is best known for collaborating with?
Born Again (Black Sabbath album): Born Again is the eleventh studio album by English heavy metal band Black Sabbath, released in August 1983. Born Again (Black Sabbath album):  It is the only album the group recorded with lead vocalist Ian Gillan, best known for his work with Deep Purple. Deep Purple: Deep Purple are an English rock band formed in Hertford in 1968.
1968