One is loath to call a new Greubel Forsey timepiece their “most ambitious yet” because the company seems incapable of producing anything unadventurous, safe or conventional. But a GF mash-up? To satisfy the claim of “four tourbillons orbiting the Earth”, Robert Greubel and Stephen Forsey have married their second Fundamental Invention, the Quadruple Tourbillon, with their three-dimensional take on the GMT, a solution that features an outsized, detailed, rotating globe.

A dream timepiece for the jetsetter, the GMT displays three timezones as well as a universal time function. As complications go, this is as useful as can be in the modern era of international flight as a common occurrence. But the company’s speciality, whatever other complications or devices it may master, is the tourbillon, conceived by Abraham-Louis Breguet over 200 years ago as a means of eliminating the effects of gravity on a watch’s timekeeping.

His answer to the problem was to house the regulating organ of a watch – its hairspring, balance wheel and escapement – within a rotating cage. With this assembly turning around on its own axis, usually completing the revolution in one minute, the elements subject to the pull of gravity would experience constantly changing positioning, thereby averaging out timing variations.

For Robert Greubel and Stephen Forsey, their life work has been to “re-imagine the tourbillon principle”, leading to their first three Fundamental Inventions: the Double Tourbillon 30° (2004), the Quadruple Tourbillon (2005) and the Tourbillon 24 Secondes (2006). Now, in the GMT Quadruple Tourbillon, they have chosen to combine their second invention with a multiple timezone display.

Further refining the concept of the tourbillon, Greubel and Forsey believe that the more different positions the regulating organ undertakes, the more precise the timekeeping will be. This involved the invention of a spherical differential, but coupling four separate tourbillons would have been challenging, especially in the confines of a wristwatch case.

To facilitate this need for compactness, and to save space in all three dimensions, they cleverly constructed the tourbillons in pairs, devising a unique system of compact cages. As the Greubel Forsey Inventions complement each other, the pair modelled their solution on the Double Tourbillon 30°, its first cage rotating in one minute and angled at 30°, fitted inside a second upright cage which completes its full rotation in four minutes. When combined, the inclination of the inner cage and the different rotational speeds of the two cages cancel out the timing variations due to the earth’s gravitational attraction, exploiting all the positions a wristwatch can adopt.

Upon bringing the Quadruple Tourbillon and the GMT mechanisms together, the maison developed a new hand-wound calibre comprising 805 parts, including three fast-rotating barrels; this would endow the timepiece with a generous 72-hour power reserve. Its hours/minutes dial is positioned between 1 and 2 o’clock, enjoying the prominence any watch’s main function merits. Located at 4 o’clock are the coaxial small seconds and second timezone display, adjustable in one-hour increments by means of a pusher.

Sited between 8 and 9 o’clock is the sublime three-dimensional globe, constantly rotating and surrounded by a fixed ring with 24-hour indications to display local time for all the longitudes, while also showing day or night. Also showcased are the four tourbillons in two pairs on either side of the globe, on full view in their own apertures. Each is secured to black-polished bridges with gold chatons and exhibiting hand-polished bevelling and countersinks.

Turning over the timepiece reveals the universal time display, with its fixed 24-hour scale showing day/night zones; a disk with three-letter abbreviations of 24 cities identifies the various timezones. Moreover, this segment also distinguishes between the timezones that implement Summer Time (Daylight Saving Time), with the zones appearing in a light colour or on a dark backdrop as appropriate.

Greubel Forsey will produce only 66 GMT Quadruple Tourbillons. The first edition of 11 will be made in white gold, numbered from 1 to 11 on a plate in the centre of the dial.