 Production was delayed by the outbreak of the First World War in 1914, and the first N class rolled out of Ashford Works in 1917, three years after design work was completed.The class replaced obsolete 0-6-0s as part of the SECR's fleet standardisation, as they used parts interchangeable with those of other classes.Eighty N class locomotives were built in three batches between the First and Second World Wars.