A hardcore V8-powered version of the Land Rover Defender is inbound as the first in a line of top-flight flagships dubbed 'Octa'.

Previously thought to carry the long-dormant SVX branding, the radical new off-roader has been spotted testing several times, but only now – a few months before its debut – has the firm given the first official details of the new model.

It will be the first car to wear the new Octa badge, which JLR says will be used for all future range-topping Defender models. The name is said to come from the octahedron shape of a diamond, the hardest naturally occurring mineral on Earth - a reflection, no doubt, of both the car’s durability and price. 

Technical details remain largely under wraps, but JLR has confirmed the new variant will use a twin-turbocharged V8 rather than the supercharged 'AJ' unit in the existing eight-cylinder Defender models. 

It is likely to be the 4.4-litre BMW-sourced unit used in various Range Rover models, including the Sport SV. In that car, it puts out 626bhp and 590lb ft, and propels the 2.5-tonne SUV to 62mph in just 3.8sec.

Using the BMW engine would suggest that the long-running 'AJ' V8 is not long for this world. Autocar previously reported that AJ production ended last year, and that JLR retained a stockpile of supercharged 5.0-litre units, of indeterminate quantity. How many remain is unclear, but the AJ is currently offered in just three cars: the Defender V8, the Jaguar F-Pace SVR and the final Jaguar F-Types. Production of the latter ends for good this June.

JLR has also revealed that the Octa will use the same ‘6D Dynamic’ suspension system as the Range Rover Sport SV. This system hydraulically links the dampers front to rear as well as side to side, providing active control over the car’s pitch and roll without a physical anti-roll bar. That should help to provide the level of wheel articulation required by a hardcore off-roader like the Octa, without compromising on-road drivability or comfort.

To that end, Defender said it is testing the car in the “most exhaustive” range of conditions of any of its cars to date; “from the snow and ice of Sweden to Dubai desert, Nürburgring Tarmac and Moab rock crawls”.

Images published by the firm reveal that the Octa also receives a bespoke set of Brembo brakes, suggesting on-track performance is a priority. These are marked with the special Octa diamond logo, which also features on the steering wheel and side-pannier mounts.

The Defender Octa will be revealed in full later this year. Pricing has yet to be detailed, but the similarly conceived Range Rover Sport SV costs nearly £85,000 more than the luxurious Autobiography model, hinting at the kind of mark-up that could be applied to the Octa. For reference, the current top-of-the-line Defender 90 – the V8 Carpathian Edition – is priced from £114,975.