COMPOUNDCRS["MRH21 Grid + ODN height",
    PROJCRS["MRH21 Grid",
        BASEGEOGCRS["MRH21-IRF",
            DATUM["MRH21 Intermediate Reference Frame",
                ELLIPSOID["GRS 1980",6378137,298.257222101,
                    LENGTHUNIT["metre",1]]],
            PRIMEM["Greenwich",0,
                ANGLEUNIT["degree",0.0174532925199433]],
            ID["EPSG",9866]],
        CONVERSION["MRH21-TM",
            METHOD["Transverse Mercator",
                ID["EPSG",9807]],
            PARAMETER["Latitude of natural origin",52.3,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8801]],
            PARAMETER["Longitude of natural origin",-1.8,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8802]],
            PARAMETER["Scale factor at natural origin",1,
                SCALEUNIT["unity",1],
                ID["EPSG",8805]],
            PARAMETER["False easting",227286.9881,
                LENGTHUNIT["metre",1],
                ID["EPSG",8806]],
            PARAMETER["False northing",265751.2874,
                LENGTHUNIT["metre",1],
                ID["EPSG",8807]]],
        CS[Cartesian,2],
            AXIS["(E)",east,
                ORDER[1],
                LENGTHUNIT["metre",1]],
            AXIS["(N)",north,
                ORDER[2],
                LENGTHUNIT["metre",1]]],
    VERTCRS["ODN height",
        VDATUM["Ordnance Datum Newlyn"],
        CS[vertical,1],
            AXIS["gravity-related height (H)",up,
                LENGTHUNIT["metre",1]]],
    USAGE[
        SCOPE["Engineering survey and topographic mapping for railway applications."],
        AREA["United Kingdom (UK) - on or related to Midland Rail Hub, covering routes through Cardiff, Bristol, Gloucester, Derby, Birmingham, Leicester, and Lincoln."],
        BBOX[51.35,-3.27,53.26,-0.36]],
    ID["EPSG",9870]]