 In 1875, again at the invitation of the Prince of Wales, he joined HMS Serapis, which conducted the Prince on an official tour of India, 1875 – 76. Louis sketched some of the events of the tour and his drawings were published in the Illustrated London News. He was promoted to lieutenant on 15 May 1876. The Prince asked Louis to stay with him at Marlborough House for the summer of 1876, but wishing to gain further experience at sea, Louis instead accepted an offer to join Prince Alfred, Duke of Edinburgh, as a lieutenant on board HMS Sultan. In addition to acting as the Duke's equerry, Louis continued his naval duties. He did not enjoy the position, as the Duke was rather touchy and Louis's cabin was infested with rats, one of which he caught with his bare hands as it ran across his chest as he lay in bed. The Sultan toured the Mediterranean from July 1876.
