We have used William Herschel Telescope/INGRID Ks images on two high-latitude fields, the Coppi and Groth strips, to obtain galaxy number counts over ~180 arcmin2, to a depth of Ks~21.0. Detection efficiency corrections as a function of object size have been calculated on each pointing. We have used a signal-to-noise threshold in two complementary half-exposure images to remove spurious detections. Our data cover the range from Ks=14.5 to Ks=21.0, so they are useful for investigating a previously reported change in the number count slope (dlogN/dm) at K~17. We find a slope γb=0.54-0.63 for K<17.5 and a slope γf=0.25-0.29 for K>17.5. A total contribution from galaxies to the extragalactic background light (EBL) in the K band of νIν=10.5 nW m-2 sr-1 has been calculated. This K-band EBL coming from galaxies accounts for only ~50% of the recent measurements of the diffuse EBL. Standard number count models fail to reproduce the observed slope change at K~17.5 unless elliptical and spiral formation is pushed to z<~2. Based on observations made with the William Herschel Telescope, operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.