He left New Zealand to join the Royal Navy Patrol Service in November 1916 and in November 1917 he was promoted to Chief Motor Mechanic. He served on various Motor Boats such as the Hermione, Victory and Arrogant. In 1918 Roy Alexander was serving at Dunkirk, assigned to rescue work, making smoke screens and laying smoke floats for the raids launched at Zeebrugge and Ostend. During the raids on the 22-23 April 1918 one of the largest carried out by the Royal Navy Patrol Service (RNPS) Roy Alexander was awarded the Distinguished Service Medal. Unfortunatley Roy was wounded during the raid and died as a result of his wounds in South End Hospital in England. He is buried in the Southend on Sea Cemetrey.
Vice Admiral Roger Key praised the efforts of the RNPS that supported the warships duting the operations making a point to note 'the skills and coolness of the men who manned these craft while under heavy fire'.
The link below is to an article on Roy Alexander in the White Ensign Magazine. Next to the article on Alexander is another interesting article worth reading.