Now there are four. Audi, Porsche and Toyota are reasonably known quantities for the 83rd 24 Hours of Le Mans, which takes place on June 13-14, but into the manufacturer-dominated LMP1 pack, Nissan slips the wildest of wild car(d)s, in the stubby shape of the GTR-LM Nismo.  This group, from which the outright winner will emerge, already perms large and small capacity diesel and petrol engines, and battery, flywheel, supercapacitor and exhaust-energy-retrieval hybrid systems, usually with drive to all four wheels. Now, LMP1 returnee Nissan throws in the kind of curve ball made possible only by Le Mans’ uniquely innovation-friendly philosophy – a hybrid with top-side of 1,000bhp, but with its engine in the front and predominantly front-wheel drive.  The three incumbents are, respectively, defending Le Mans champion, all-time Le Mans-win record holder, and reigning World Endurance champion. But while the 2015-spec Porsche has indeed beaten Audi to pole in the opening two rounds of the World Endurance Championship, at Silverstone and Spa, the relentlessly reliable and similarly upgraded Audi has again outwitted the rest to win twice, with Toyota looking oddly out of sorts.  The Nissan, meanwhile, has evolved from zero in only 14 months, and as well as being way out on the conceptual limb has had a worryingly short and troubled test programme. But if it works, it would rewrite the script, yet again. That’s the back-story.  The first Le Mans test, on May 31, should have given us a foreword, but didn’t. The two-by-four-hour test isn’t mandatory, but is essential, so the whole cast was on stage as we waited for preliminary skirmishes. Then the fickle finger pointed at the skies, which chucked the spanner with sporadic and rhythm-breaking rain.
Audi, Porsche and Toyota are joined by Nissan for the 83rd running of the world's greatest endurance race. With the cars looking faster than ever after the first official practice, Brian Laban checks out the form guide