Passage: HMS Nelson (pennant number 28) was one of two Nelson-class battleships built for the Royal Navy between the two World Wars.  She was named in honour of Horatio Nelson, 1st Viscount Nelson the victor at the Battle of Trafalgar. The Nelsons were unique in British battleship construction, being the only ships to carry a main armament of 16 inch (406mm) guns and the only ones to carry all the main armament forward of the superstructure. These were a result of the limitations of the Washington Naval Treaty. Commissioned in 1927, Nelson served extensively in the Atlantic, Mediterranean and Indian oceans during the Second World War.  She was decommissioned soon after the end of the war and scrapped in 1949. She was nicknamed "Nels-ol" from the resemblance in her outline to RN oilers, whose names ended in "-ol".

Question: How many Nelson-class battleships were created for the Royal's Aquatic Military Branch?
two