Voices in the Dark — Edmund Cooper

At ten-thirty in the morning the skies over London were clear. Then an arrow formation of five bright points became visible. They appeared to be moving at an amazing speed in tight circles. They were spiralling down to about five thousand feet, and at that altitude their nature was easily discernable. They were the tings most of us had discussed and dismissed at one time o another. Flying Saucers. Giant saucers, smooth and lustrous and blinding, more than a hundred yards in diameter. They hung over the city in a neat formation.