Current Imaging Atmospheric Cherenkov Telescopes (IACTs) have only recently begun to detect very-high energy emission (VHE; >100 GeV) from Gamma-Ray Bursts (GRBs). Here we report on the observations of the extremely bright and rather nearby GRB 180720B by the High Energy Stereoscopic System (H.E.S.S.), leading to its detection in the 100–440 GeV energy range. This detection was achieved over 10 hours after the end of the prompt gamma-ray emission phase, which was seen by Swift-BAT, Fermi-GBM and LAT. We will present the VHE late-time detection in the context of observations at lower energies, discussing possible scenarios for the radiation mechanisms at work. Finally, we will stress how this VHE detection is crucial for future IACT facilities, leading to a considerable revision of their GRB-detection rate estimate.