Pulling a fully loaded GLS onto a motorway and pressing the accelerator reveals something that feels almost incongruous for a seven-seat luxury SUV of this size: there is genuine urgency here, the kind that comes from 700 Nm of torque arriving early and staying. The 400d's 3.0-litre inline-six diesel sends 330 HP through a nine-speed automatic to all four wheels, and the AIRMATIC air suspension with adaptive damping does a convincing job of making the whole considerable mass feel settled and deliberate, whether the road is smooth or not. The AMG Line specification sharpens the exterior without making a scene, and inside the cabin is finished in premium Nappa leather with powered, heated, ventilated and memory front seats that make it easy to forget how far you have travelled. The MBUX dual HD 12.3-inch widescreen display runs the width of the dashboard in a clean, unified spread, complemented by wireless Apple CarPlay and Android Auto, a Burmester surround sound system, a wireless charging pad and ambient lighting that can be adjusted to suit the mood of the journey. A panoramic sunroof, third-row seating, a 360-degree camera and the full suite of driver assistance including adaptive cruise control complete a specification that requires very little imagination to live with. Sourced from the Japanese domestic market, this is a GLS that arrives with the kind of care and specification that makes it a straightforward choice in a segment where compromises are usually the norm.