Remote Radar Head Saxa Vord, also known as RAF Saxa Vord, is a Royal Air Force radar station located on Unst, the northernmost of the Shetland Islands in Scotland. The station's motto is 'Praemoneo de Periculis' ('I warn of danger'). The site was named after Saxa Vord, the highest hill on Unst. The island of Unst has been important in UK defense since World War II, with two radar sites by 1945. The site at Saxa Vord hill was selected for a new long-range radar as part of the post-war ROTOR network, receiving AMES Type 14 and Type 13 radars. Installation of the more powerful AMES Type 80 began in 1955, which was later rebuilt inside a radome after wind damage. No. 91 Signals Unit formed at Saxa Vord in 1957 and was declared operational the same year. During its early days, the site was shared with the Royal Navy. In the Linesman era, the station retained its Type 80, later introducing the AMES Type 96 (Marconi S649) and Plessey HF200 in 1976. The station was renamed Royal Air Force Saxa Vord in 1984. In 1993, the IUKADGE system was implemented at Saxa Vord, which included an AMES Type 93 radar, funded by NATO. Around 2000, the station operated as Remote Radar Head (RRH) Saxa Vord, controlled by RAF Buchan, and was upgraded to a fully staffed station in 2004. RRH Saxa Vord closed in April 2006 due to the obsolescence of the Type 93 radar and a reduced threat environment, with the radar being dismantled for spares. In September 2017, the Ministry of Defence confirmed a £10 million investment to reactivate the site as a Remote Radar Head to enhance coverage of northern UK airspace, in response to increased Russian military activity. Work began in October 2017 to relocate a Lockheed Martin AN/TPS-77 L-band radar to Saxa Vord. The new radar achieved initial operational capability in January 2018. As of July 2019, it is a fully operational radar station. The MOD initiated the HYDRA program in 2020 to upgrade RRH sites, including Saxa Vord, with new communications buildings, radar towers, and perimeter security. The station is operated by the Royal Air Force, under No. 1 Group (Air Combat), and is occupied by Radar Flight (North). No personnel are permanently based at Saxa Vord, but regular maintenance visits occur.