David Cameron had previously ruled out holding a second referendum, calling it "a once-in-a-lifetime event".<unk> Complete the following sentence: David Cameron had previously ruled out holding a second referendum, calling it "a once-in-a-lifetime event". <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk>
2009 <unk> <unk>