The 2018 Blackett Report, the UK Government’s study of critical dependencies on satellite-derived time and position, focused on improving the resilience of services that depend on Position, Navigation and Timing (PNT). It concentrates on Critical National Infrastructure (CNI) and seeks to support future applications. The recommendations of the review called, for inter alia: • operators of CNI to make provision for the loss of Global Navigation Satellite Systems (GNSS) by employing GNSS-independent back-up systems; and • the specifying of consistent requirements that encompass the GNSS and PNT system parameters of accuracy, availability, integrity and continuity. A report sponsored by Innovate UK estimated that a five-day total outage of GNSS would cause an economic loss to the UK of the order of £5.2 billion. Of this, 21% would be attributable to the maritime sector, including shipping, ports and supply-chain logistics. This maritime sector contains some of the foremost professional adopters of GNSS. It is one of the most GNSS-dependent sectors; however, it is also one of the most aware of GNSS vulnerabilities and their consequences, since extensive studies of GNSS resilience have focussed on maritime use. The MarRINav (Maritime Resilience and Integrity of Navigation) project encompasses the recommendations of these previous studies and those of the Blackett Report. It lays the foundations for the UK’s future CNI in respect of PNT resilience and integrity (R&I) . The work seeks to mitigate the effects on the maritime sector of GNSS denial, at the same time providing technical guidance for other sectors. To this end, a wide range of options for infrastructure and services to support UK ports and maritime operations have been investigated, each of which is complementary to GNSS. In this way, the project has identified improvements to PNT R&I in current and emerging applications. With GNSS remaining at the core of navigation and timing, the project investigated how these complementary systems can be integrated with GNSS and one another, the whole providing truly resilient PNT, not only for the maritime world but also potentially across multiple sectors of CNI. References:  Government Office for Science, ‘Satellite-derived time and position: A study of critical dependencies’, HMG, London, UK, Jan. 2018.  London Economics, ‘The Economic impact on the UK of a disruption to GNSS’, London, UK, Jun. 2017.