The company has been the subject of several undercover investigations since 1989. Sarah Kite of the British Union for the Abolition of Vivisection (BUAV) secured a job and filmed inside HLS in 1989. Zoe Broughton did the same for Channel 4 in 1996, as Michelle Rokke claimed to have done for PETA in 1997. Lucy Johnston for "The Daily Express" gained access in 2000. A diary kept by Kite, who worked undercover there for eight months, alleged that HLS workers routinely mishandled the animals, shouting at them, throwing them into their cages, and mocking them for having fits in response to toxicity tests. In 1997, Zoe Broughton came out with footage showing puppies being hit and shaken. A year later, Michelle Rokke allegedly obtained footage of the vivisection of a monkey in HLS in New Jersey, in which a technician expresses concern that the animal is inadequately anaesthetized. Between 2006 and 2008, an Animal Defenders International employee filmed undercover inside HLS after securing a position inside its primate toxicology unit in Cambridgeshire.