[3] In 1856, thrown on his own resources after his father's death, Shelford left Glasgow for London, and in December of that year he entered the office of John Fowler as an assistant engineer, remaining there until 1860.
Leaving Fowler's service in the autumn of 1860, Shelford became an assistant to F. T. Turner, joint engineer with Joseph Cubitt on the London, Chatham and Dover Railway.
[3] After employment on surveys Shelford was appointed resident engineer on the high-level railway to the Crystal Palace, the Act of Parliament for which was passed in 1862.
In 1862–5 he was also engaged, under Turner, as resident engineer on the eastern section of the London, Chatham and Dover Railway, to Blackheath Hill.
[3] In 1865 Shelford started practice on his own account in partnership with Henry Robinson, later professor of engineering at King's College, London.
The work carried out by the firm during the next ten years included the railways, waterworks, sewage-works and pumping- and winding-engines, and shafts for collieries and mines at home and abroad.
In 1869 he visited Sicily and installed machinery and plant for sulphur mines there; for his services he was made a chevalier of the Order of the Crown of Italy.
A short railway, six miles in length, from Sierra Leone to the heights above Freetown, was opened in 1904, and road-bridges were built to connect the island of Lagos with the mainland.
[3] In 1869 Shelford presented to the Institution of Civil Engineers a paper On the Outfall of the River Humber, for which he received a Telford medal and premium.
At the British Association Shelford read two papers, in 1885 on Some Points for the Consideration of English Engineers with Reference to the Design of Girder Bridges, and in 1887 on The Improvement of the Access to the Mersey Ports.