The Hitchhiker’s Guide To The Galaxy, first in the series of wacky and beloved sci-fi books by Douglas Adams, turns 42 years today. And of course 42 is the answer to the answer to the ultimate question of life, the universe and everything.

The Marcus O'Dair, author of The Rough Guide to the Hitchhiker’s Guide to the Galaxy.

We can see it in culture, where Adams' story is rumoured to have inspired everything from the band Level 42 to comedy show The Kumars at No. 42,“ he says. "We can see it in tech: in the real-life ‘knife that toasts,’ for instance, or in-ear translation services reminiscent of the Babel fish. The most visible sign of its ubiquity, though, might be the fact that we can celebrate its anniversary not at 40 or 50 years but at 42 — and everyone knows why.

Don’t panic - and never leave home without a towel.