Born on 9 July 1869 at Ballycogley Castle, Co Wexford, the second son of Richard Cherry Sikes, of Cork, and Susannah Lecky Jacob, his wife; he was educated privately. He received his medical training at St Thomas's Hospital, where he won an entrance scholarship and the Tite and Peacock scholarships. He won gold medals at the intermediate and final MB examinations, and won the Treasurer's gold medal, the Bristowe medal, and the medal in medicine. He served as medical registrar at the Hospital in 1900. Sikes was particularly interested in physiology and made postgraduate studies at St Bartholomew's and at Marburg University. He took the Fellowship and the London MD in 1898, and in 1900 the Membership of the College of Physicians. He was for several years lecturer in physiology at King's College, Strand, and published some valuable physiological papers. He took the DSc London in 1906. Sikes became a part-time assistant medical officer in the newly formed school medical section of the public health department of the London County Council, under Dr James Kerr, in 1908; he was appointed one of the original whole-time divisional officers in 1912, and was in charge of the north-western division until his retirement in 1935. During the war of 1914-18 he was surgeon to an ambulance train in France. Sikes married in 1902 Mary Maitland, eldest daughter of Thomas Townshend Somerville, a descendent of two distinguished Co Cork families. While working in London he lived at Moat House, Langley, Bucks, but retired to Porthcurnick, Portscatho, Cornwall, where he was able to indulge his taste for gardening. He died there on 25 May 1948, aged 78, survived by his wife and one son; their other son had died before him. Mrs Sikes died at Truro on 10 May 1952. Sikes was renowned among his friends for his mordant Irish wit.