I searched for Sir Stephen Pigott on the internet and found this link, also copied below. Sir Stephen was the managing director of John Brown and Co., Ltd, shipbuilders until his retirement in 1948.
Sir Stephen, who was born in 1880 in Cornwall, New York, took a leading part in the building of the two great liners, Queen Mary and Queen Elizabeth.
After reading his obituary, I guess he was on his honeymoon with the second Lady Pigott, on this voyage.