Oswald Stevens Nock was the first son of Samuel James Nock and his wife Rose Amy (née Stevens). Born in Sutton Coldfield, his father became manager of a bank in Reading soon after Oswald's birth, and as a young child he was regularly taken in his pushchair to both the GWR and SECR lines that served Reading.

From 1913, young Oswald attended Marlborough House and then Reading School, before becoming a boarder at Giggleswick School in 1916 when the family moved to Barrow-in-Furness. Despite moderate performances in maths and science, Nock passed his school certificate and London matriculation examinations in 1920, and entered the City & Guilds Engineering College in London the following year. In 1924 he was awarded a BSc and having made unsuccessful applications to the GWR, Vickers at Barrow, and Armstrong Whitworth he became a graduate trainee at the Westinghouse, Brake, and Saxby Signal Co. Ltd the following year.

When Nock joined, Westinghouse was enjoying much work with the newly formed "Big Four" in moving from mechanical signalling to electrically controlled systems, however the early 1930s saw a slump in work with many there fearing for their jobs. To supplement his income Nock took a correspondence course in journalism after answering an advertisement entitled 'More Profit from Writing'. His first article was entitled 'Carlisle, a Station of Changes' and appeared in the Railway Magazine in January 1932. He had more success soon after when a mini-feature entitled ‘Hyde Park's ghost trains’ appeared in the Evening News. Over the following 2 years Nock had 16 articles published, but he was concerned that either his writing or his job would be jeopardised if he was published under his own name, so everything except contributions to the Railway Magazine, which was considered something of a joke in some professional circles, was written under a pen name; often using his second name of Stevens prefixed by two letters CK from his surname, or under the pseudonym of 'Railway Engineer'. Nock also worked to develop his writing skills away from Railway subjects and through his love of the country and keenness on purely pictorial landscape photography he found an occasional market in The Motor. Articles such as 'A Lonely Scottish Lido', 'The Gateway of the Lakes' and 'The Country of St Abb' appeared, despite Nock not owning a car. Nock himself considered the article 'Autumn in Moidart' which appeared under his own name in the Glasgow Herald in November 1934 to be his best, but after this writing about Railways began to take off.

On 15 May 1937 Nock married Olivia Hattie Ravenall at Bushey parish church before taking her on honeymoon on the Flying Scotsman. They settled in a large house on Sion Hill, Bath, where they had a daughter and a son. It was here that Nock created an O gauge model railway with twenty-three hand-built locomotives.

Nock authored more than 140 books and 1000 magazine articles, which are often considered to be less than authoritative because of his voluminous output. He tended to re-use data, text and anecdotes in different books, including paragraphs culled in their entirety (check similarities in "Steam Locomotive" 1957 & "British Steam Railways" 1962). Having said that, Nock's style is easily read and he explains engineering issues in layman's terms, making the subject more accessible. His continuation of E. L. Ahrons' work, continuing steam locomotive development from 1925, is much more friendly to the layman or armchair enthusiast than Ahrons' seminal work "The British Steam Railway Locomotive Volume 1 From 1825 to 1925". If his work is treated as a general picture of railways in action, from the personal viewpoint of someone who was there and who interacted with railway personnel at various levels, both professionally and in his leisure time, his output is reasonably valid. One of his most famous books was 'The Pocket Encyclopedia of British Steam Railways and Locomotives'

In the 1960s and the 1980s he lived in Batheaston, near Bath.