SED data for one example system, HD 37484 (Sect. 2.2.3). Black circles show photometric data, triangles are upper limits, and the grey shaded region is the Spitzer/InfraRed Spectrograph (IRS) spectrum. The best-fit model (black line) comprises the stellar flux (dotted green line) plus additional emission from two debris discs: a cold disc with blackbody temperature 60 ± 7 K (dashed blue line) and a warm disc with blackbody temperature 130 ± 10 K (dash-dot red line). This paper considers only the outermost (cold) discs.