However, he warns that advertising our presence could be risky. “We might like to assume that if there is intelligent life out there it is wise and benevolent,” he said. “But of course we have no evidence for this…

The astronomer Heather Couper said: “My main worry is that our technology is simply not up to the task. Earth came into existence four to five billion years ago, but the oldest stars are twice that age. They may have life, but that life may be far more advanced than we are.”

Others suggest aliens may have good reason not to give away their presence. Weak electromagnetic signals have been transmitted from Earth for nearly a century in the form of radio, television and other transmissions. By now some should have travelled 100 light years out into space, though they will be growing fainter and fainter.

If aliens have picked up footage of, say, Bernard Manning or Simon Cowell, let alone the second world war, they may have decided to keep quiet. “They may be very like us,” said Conway Morris. “I’m not sure I’d answer the telephone.”