These two books are about aliens – intelligent beings who may or may not have visited our planet. Jonathan Caplan is a distinguished lawyer and believer; David Lavelle is a journalist and sceptic.

Aliens have always been with us. For at least 4,000 years there have been reports of strange visitations assumed to come from heaven, hell or simply the universe. Angels and demons were commonplace, but they were eventually replaced by technology-based visions, most often flying saucers. These could be quietly ignored until 1947, when postwar alien fever was sparked in Roswell, New Mexico. Metal and rubber debris were found which the US army initially claimed were parts of a ‘flying disc’. The story raced round the world, but the official explanation was rapidly retracted and the disc was reidentified as a weather balloon. This made matters worse. Clearly, said the true believers, this was a blatant cover-up and, over the ensuing decades, worldwide, though primarily in America, alien freaks kept the Roswell flame burning.

The release of millions of pages confirming the reality of aliens has been banned by the US government

Not for Disclosure offers the most persuasive defence yet of the cover-up theory. For Caplan, the aliens are definitely out there. ‘The collective force of the evidence contained in these pages will be a shock to most,’ he writes. That’s not what one might expect from an internationally respected lawyer, a King’s Counsel. But he has done the work: ‘This book is the product of five decades of personal research and it provides access to some of the vast body of material, much of it not readily available.’