In July 2000, he was the Detective Inspector on Highdown Division who dealt with the disappearance of missing child Sarah Payne, who went missing in Littlehampton on the evening of 1 July. Detective Inspector Underhill was appointed as the Deputy SIO (Senior Investigating Officer) of the enquiry, which became a murder investigation after a body was found near Pulborough on 17 July and identified as that of Sarah Payne the following day. Underhill remained on the investigation until Roy Whiting was convicted of Sarah Payne's murder in December 2001 and sentenced to life imprisonment. This alert system is based on Megan's Law in America. Underhill later took this to the Association of Chief Officers (ACPO) Homicide Working Group to ask for the pilot to be introduced nationally, which was achieved by 2006. Underhill was also an adviser [for one day] in the case of Holly Wells and Jessica Chapman, who were abducted and murdered. He then moved to the Training Department in Sussex Police, having qualified as a police trainer, assessor and verifier. On retirement he moved to Dorset. Underhill went on to campaign for safeguarding issues, including Sarah's Law, which was introduced into Dorset in October 2011. Underhill became the Laymember on his Local Safeguarding Children's Board, as well as becoming a trustee for the Bournefree charity. He is a visiting lecturer at Bournemouth University for the School of Applied Science. In July 2011, Underhill reported to Operation Weeting that he thought his police phone had been hacked during the Sarah Payne murdercase. Underhill was initially contacted by a source at The Sun newspaper warning him of how they were in possession of information from a reliable source alleging an inappropriate relationship between Underhill and Sara Payne during the investigation.
