HS2-VRF height - EPSG:9303

WKT

VERTCS["HS2-VRF_height", 
	VDATUM["HS2_Vertical_Reference_Frame"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["HS2-VRF_height", 
	VDATUM["HS2_Vertical_Reference_Frame"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "9303"]]

Data from @esri/proj-codes

{
  "wkid": 9303,
  "latestWkid": 9303,
  "macro": "PE_VCS_HS2_VRF_HEIGHT",
  "name": "HS2-VRF_height",
  "wkt": "VERTCS[\"HS2-VRF_height\",VDATUM[\"HS2_Vertical_Reference_Frame\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"HS2-VRF_height\",VDATUM[\"HS2_Vertical_Reference_Frame\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"9303\"]]",
  "description": "HS2-VRF height",
  "authority": "EPSG",
  "version": "9.8.13(12.9.0)",
  "deprecated": "no",
  "areaname": "UK - London to Birmingham and Crewe",
  "extent": {
    "slat": 51.45,
    "nlat": 53.3,
    "llon": -2.75,
    "rlon": 0
  }
}