The ionisation hodoscope (IH) of the DIRAC (PS 212) experiment at CERN is optimised to separate ionisation signals produced by otherwise unresolved double tracks from ionisation signals produced by a single particle. While its total thickness is only 1.5% of a radiation length, it consists of four planes and provides two measurements of ionisation loss in each of the two projections. It suppresses the background from single-track events by a factor 50 while keeping more than 80% of double-track events. The IH design and performance during data taking in 2001–2003 are described.