Track-only model has more power, a wider body, eye-catching design, and is sold out.
The new McLarne Senna GTR is powered by the company's 4.0-litre twin-turbo V8, which has been tuned to deliver 607kW of power and 800Nm of torque.
A recalibrated control unit and the removal of the secondary catalyst are responsible for the 18kW increase over the road-going Senna.
Unlike the 2018 concept, the production version has exhaust tips at the back of the car instead of the side, as well as an enhanced aero package with new dive planes and vortex generators.
The GTR has a wider track than the regular Senna - up 77mm at the front, and 68mm at the rear - with suitably broader wheel arches to match. Overall height has been reduced by 34mm to 1195mm.
For track use the GTR has gained a roll cage, pneumatic air jacks, a pit radio, a fire extinguisher and a data logger.
Despite these additions, dry weight is down 10kg to 1188kg thanks to the deletion of airbags, the sound system and central touchscreen.
Standard features include air conditioning, active aerodynamics, pit lane speed control, anti-lock brakes, stability control, and anti-collision radar. A passenger seat is optional.
Although the GTR has been developed specifically for the track, it is not compliant with GT3 regulations, and, as such, rides on 19-inch centre-locking alloy wheels fitted with 285/650 Pirelli tyres front and 325/705 rubber at the rear.
Just 75 Senna GTR coupes will be built, all in left-hand drive. Despite the starting price of £1.1 million ($2.1 million), excluding taxes, all are spoken for.