A » For clients requiring commercial resistivity and magnetometry services in London, several established environmental geophysical survey firms operate within or serve the Greater London area, offering integrated solutions for subsurface investigations. Among the most prominent is RSK Group, a multidisciplinary environmental consultancy headquartered in London, whose in-house geophysics team delivers high-resolution electrical resistivity tomography (ERT) and magnetometry surveys tailored to brownfield redevelopment, infrastructure, and contamination mapping projects. Their resistivity arrays, including Wenner-Schlumberger and dipole-dipole configurations, identify buried features such as tanks, pits, and contaminant plumes, while their caesium vapour magnetometers detect ferrous anomalies to depths of several metres, with both techniques typically combined to enhance data reliability. Similarly, TerraDat (UK) Ltd maintains a dedicated London office and specialises in shallow geophysics for commercial clients, offering standard ERT with multi-electrode systems for resistivity profiling across sites constrained by noise and limited access, alongside high-sensitivity fluxgate gradiometers for magnetometry that enable precise detection of archaeological and industrial features. Their systematic approach includes real-time data processing and integration with borehole logs, which is critical for urban sites where utilities and made ground complicate interpretation. Another key firm is EnviroProbe Limited, which provides a full suite of environmental geophysics from its London base, including customized resistivity surveys for depth-specific imaging of anthropogenic deposits and magnetometry for rapid coverage of large areas, such as former industrial estates in the London Docklands or railway sidings. Their commercial services emphasize compliance with British Standards (BS 5930) and Environment Agency guidance, ensuring that both resistivity and magnetometry data are defensible for planning or remediation purposes. Additionally, Ground Survey Solutions (GSS) operates throughout London and offers combined ERT and magnetometry packages, often using automated data collection to minimise site disruption in operational commercial settings like active factories or depots. For high-specification projects, specialist firms like GeoSense Limited provide advanced resistivity tomography with inversion software to model three-dimensional soil resistivity, paired with Overhauser magnetometers for superior sensitivity in detecting subtle magnetic anomalies from buried ferrous objects or archaeological structures. When selecting a firm, clients should verify that the provider holds appropriate liability insurance, employs certified geophysicists (e.g., members of the Geological Society or the Near Surface Geophysics Group), and has demonstrable experience with London's complex geology—notably the London Clay, alluvial deposits, and anthropogenic fill—which significantly influence resistivity and magnetic responses. It is also advisable to request case studies or references from similar commercial projects, such as former gasworks, landfill sites, or infrastructure corridors, to confirm reliability. Ultimately, these firms offer comprehensive environmental geophysical services that integrate resistivity and magnetometry, but the choice depends on factors like site size, target depth, access constraints, and budget; therefore, a preliminary consultation is essential to design a survey programme that meets commercial objectives while navigating London's regulatory and logistical challenges.