Truth is certainly stranger than fiction in Grant Heslov’s new black comedy, The Men Who Stare at Goats, inspired by Jon Ronson’s non-fiction best-seller of the same name.

Prefaced by a disclaimer – “More of this is true than you would believe” – the film constructs a deranged tale of US servicemen who are trained to become Jedi warriors, capable of killing the enemy with mind-power alone.

The soldiers harness this extra-sensory perception and telepathy by staring for hours at goats, hanging bags of sand on parts of their anatomy that shouldn’t see the light of day in public, and telling themselves they can pass through solid objects.

Of course it’s all hogwash, but that doesn’t stop General Hopgood (Stephen Lang) rising from his desk in the amusing opening sequence, announcing loudly, “I’m going into the next office”, then running full pelt at a solid wall.

“Damn it,” he groans after the laws of physics deal the general a rude awakening and a trip to the infirmary. Heslov’s film comes close to knocking us out, too.

Reporter Bob Wilton (Ewan McGregor) is embedded in Iraq during the early years of the invasion, scrabbling around for a story. By chance, he encounters oddball Lyn Cassady (George Clooney), who makes outlandish claims about being part of the so-called New Earth Army – an experimental US military unit dedicated to the art of mental warfare.

Lyn regales Bob with tall tales of his escapades, including how he once killed a goat by staring down the cloven-hoofed beast. “Every night I would dream about that goat, opening its mouth without making a sound,” recalls Lyn sadly. “The silence of the goats,” replies Bob with a wry smile.

Lyn is on a mission to track down the New Earth Army’s one-time commander Bill Django (Jeff Bridges), who has disappeared without trace.

So Bob tags along with his mentally-unstable new acquaintance, learning more about the covert program through colourful reminiscences, such as the fierce rivalry with fellow psychic Larry Hooper (Kevin Spacey), who was always fiercely jealous of Lyn’s talents.

The mission becomes increasingly perilous, and the reporter fears for his life. “You weren’t meant to be here Bob. It’s the Jedi in you that senses that,” comments Lyn, making an inadvertent reference to McGregor’s role in the Star Wars films.

The Men Who Stare at Goats is a scatter-brained road movie in the company of another hilarious misfit from Clooney’s ever-expanding repertoire. McGregor plays the straight man throughout as our eyes and ears to the escalating madness, culminating in a memorable LSD trip in the desert.

Wherever truth ends and fiction begins, Heslov’s film is a fast-paced jaunt that doesn’t overstay its welcome, underpinned by larger-than-life supporting performances and a lively script from Peter Straughan.