Somehow, a Rivian reservation holder ended up in Ushuaia, the capital city of Tierra del Fuego and considered the southernmost city in the world, at the same time as two Rivian R1T pickups. Naturally, he walked around the vehicles snapping photos that he posted on Rivian Forums where other fans have broken down the differences between what appear to be pre-production prototypes and the concept truck.

Those who like the Rivian will be glad to see that the prototype differs only in small details from what we've seen so far, the only potentially disappointing change being the steering wheel. The concept unit with the square center and two minimalist scroll wheels on the spokes is gone, replaced by a nondescript black unit with a round center and numerous spoke controls that could have come from any sporty economy car.

Among the other changes on the flat white and flat gray pickups, it seems the front bumper fits front tow hooks where the concepts have gloss black panels. The charge port has moved from the passenger's side to the driver's side, and amber reflectors decorate the front wheel arch cladding. The cab's rear edge sports a thicker spoiler with two high-mounted brake lights and two slots to channel air down the backlight. The split rear windows of the concept are gone, replaced by a full-width window, the door handles have a slightly new design, and the side mirrors are larger. The carbon fiber inserts between the concept wheels' spokes have been removed. The rear bumper has been reshaped and looks less exciting, but more production-ready, with what could be a removable center section hiding a tow hook. The two fold-down steps under the rear bumper, said to enable easy access to the bed with the tailgate up, are also missing. Finally, the interior shows off the Black Mountain color scheme in black and gray, which will join the other two themes we know of so far, Forrest Edge and Lunar Rock.

A report on Argentina's Autoblog (no relation) says the Rivians are part of actor Ewan McGregor's and friend Charlie Boorman's next travelogue documentary. The two paired up in Long Way Round in 2004, which ran from London to New York via Europe and Asia, then followed that with Long Way Down, which ran from Scotland's John O'Groats to South Africa's Cape Town. The third piece is expected to be called Long Way Up, starting in Ushuaia and ending some 15,000 miles later at the top of Alaska. The duo looks to have given up ICE transport for on-camera work; the pair rode the BMW R1150GS in the first special, the BMW R1200GS in the second. Argentina Autoblog says the convoy it saw in Tierra del Fuego included four Harley-Davidson LiveWires, the two Rivian R1Ts, two all-wheel drive Mercedes-Benz Sprinters and a Ford F-350 dually.

Based on the interior shots of the Rivian pickups, our guess is they're tagging along with the Mercedes' and the Ford off camera, in support roles. The trip would also provide a months-long trial over some outstanding proving grounds. Rivian Forum users say the EV firm will host another event in Atlanta on September 13, perhaps we'll get more information then. For now, we gotta say the R1T looks really good with some dirt on it, and judging by this video on Twitter, Rivian buyers won't need to rush out and buy a light bar to go off-road. Head over to Rivian Forums to check out more images and comparison shots.