For a start, it’s the biggest. The Antwerp races combined gathered 3,600 entries, while the Brussels marathon/half marathon last October got around 8,800. Yet the 20km of Brussels issues 30,000 numbers – and even that is well under the number of applications that it receives. (Safety and logistical concerns mean organisers have had to put a ceiling on numbers.) Indeed, in recent years there has been a surge in applications due to the rise of charity runs – pioneered by the London Marathon – and the increasing efforts by businesses to use the event as a staff team-building initiative.

The scale is reflected everywhere in the event, which takes in a momentous route along city landmarks and leafy avenues. It starts and finishes in the Jubelpark, an epic setting for any race, and thunders up Wetstraat, past the Royal Palace, up towards the law courts, down the length of Louizalaan, into the Kamerenbos, along Franklin Rooseveltlaan and Vorstlaan and, finally, back towards town past Woluwepark and up the fearsome hills of Tervuurselaan.

The massive organisation involves diverting traffic, generating sponsorship, ensuring medical facilities along the route, forging all those medals and distributing some 150,000 plastic bottles of water (and clearing them all up by 19.00, four hours after the start of the race). Their responsibilities include how to manage the 750 volunteers, where to put the 30 bands that play along the route and how to process the results of the 25,000 or so who complete the race.

The first edition in 1980, gathering 3,500 runners at the Heizel stadium, was indulged by the Brussels authorities, who assumed it would never become more than a one-off event. It is now the highlight of the Belgian running calendar, which may well clog up the roads for a few hours, but will provide an extraordinary challenge to thousands.