English singer-songwriter Sam Smith held onto the number one spot in Britain’s album charts on Sunday, seeing off a strong challenge from Led Zeppelin frontman Robert Plant, the Official Charts Company said. Plant’s new release, “Lullaby And The Ceaseless Roar”, his 10th solo outing, rocketed to number two, making it the highest new entry. The Official Charts Company said it had topped the chart all week “until the eleventh hour” when it had been “pipped to the post.”