Black holes have been found over a wide range of masses, from stellar remnants with masses of 5-150 solar masses (M(☉)), to those found at the centres of galaxies with M > 10⁵M(☉). However, only a few debated candidate black holes exist between 150M(☉) and 10⁵M(☉). Determining the population of these intermediate-mass black holes is an important step towards understanding supermassive black hole formation in the early universe^(1,2). Several studies have claimed the detection of a central …