on behalf of astronomers who do not travel to the telescope) has been considered and rejected on scientific and operational grounds. Instruments The WHT is equipped with a wide range of scientific instruments, providing a range of capabilities to astronomers. , the common-user instrumentation is: ACAM Auxiliary-port CAMera – optical imager/spectrograph, with broad- and narrow-band imaging over an 8' field and low-resolution (R < 900) spectroscopy. Permanently mounted at one of the broken-Cassegrain foci. ISIS Intermediate dispersion Spectrograph and Imaging System – medium resolution (R = 1,800-20,000) long-slit dual-beam optical spectrograph. Mounted at Cassegrain focus. ISIS was one of the original first generation of WHT instruments. LIRIS Long-slit Intermediate Resolution Infrared Spectrograph – near-infrared imager/spectrograph, with imaging over a 4' field, spectral resolutions R = 700–2500, spectropolarimetry, and long slit and multi-object slit-masks. Mounted at Cassegrain focus. WEAVE WHT Enhanced Area Velocity Explorer - a multi-object optical spectrograph, which uses a robot positioner and optical fibres to observe up to 1000 targets at a time. Beginning in 2022, 70% of the telescope's time will be dedicated to surveys with WEAVE. Prior to the installation of WEAVE (2020-22), ISIS and LIRIS were the workhorses of the WHT, with approximately two-thirds of all time awarded using those two instruments. In addition the WHT is a popular telescope for single-purpose visitor instruments, which in recent years have included PAUCam, GHαFaS, PNS, INTEGRAL, PLANETPOL, SAURON, FASTCAM and ULTRACAM. Visitor instruments can use either the Cassegrain focus or one of the Nasmyth foci. A common set of calibration lamps (Helium and Neon arc lamps, and a Tungsten flat-field lamp) are permanently mounted at one of the broken-Cassegrain foci, and can be used for any of the other instruments. Scientific research Astronomers use the WHT to conduct scientific research across most branches of observational astronomy, including Solar System science, galactic astronomy, extragalactic astronomy and cosmology. Most of the instruments are designed to be useful for a range of different research. The WHT has been used to make many significant new discoveries. Some of the more notable include the first evidence of a supermassive black hole (Sgr A*) at the centre of the Milky Way (in 1995) and the first optical observation of a gamma-ray burst (GRB 970228) (in 1997). Since the mid-1990s the WHT has faced increasing competition from newer telescopes. Nevertheless, a wide range of research continues to be done with the telescope. In recent