HSC.
image by Jarig Bakker, None
The flag is yellow with a white diamond containing black HSC letters. The National Maritime Museum example is dated about 1951.
The early publications label this livery tankers. Its funnel was still used on Otterhound in a starboard photograph of 3 May 2012; another photograph shows an unidentified blue swallowtailed flag.
The 1942 source labels this funnel tankers but also supplies an unrelated funnel number under the company. The 1942 and 1944 publications list the livery under both Hadley and Immingham Agency, without naming the latter beside the actual illustration.
Stewart also gives this livery for Houlder Brothers. The funnel is confirmed on Cymberline in a port-side photograph of 21 February 1981.