From Graces Guide
Francis H. Trevithick (1812-1877) was one of the first locomotive engineers of the London and North Western Railway (LNWR).
Born in 1812 the fifth of six children of Richard Trevithick and Jane Harvey of Hayle
1832 He began the study of civil engineering around 1832
By 1840 was employed by the Grand Junction Railway (GJR).
1840 Appointed resident engineer on the GJR between Birmingham and Crewe
1841 Appointed Locomotive Superintendent of the GJR at Edge Hill railway works, Liverpool.
"It may interest your readers to learn that Francis H. Trevithick was appointed to the position of superintendent of the locomotive engine department of the Grand Junction Railway in February 1841, and that from the opening of the works in that year 1843 until 1857 he was the one and only chief mechanical engineer at Crewe and was responsible for the design and construction of the locomotives as well as he discipline of the department. The first entirely new locomotive engine constructed at Crewe was completed on February 20th 1845, and was No. 49 Columbine, a 6ft passenger engine. This engine had been preserved at Crewe and is now to be seen at Wembley, and it bears a plate affixed to it, stating that F. H. Trevithick was then chief mechanical engineer. The position held by Alexander Allan was that of foreman of locomotives at Crewe, and when he resigned in September, 1853, his salary was £500 per annum. His successor was the foreman from the Preston shed, who was succeeded by the foreman from the Carlisle shed, These particulars are taken from official records and are therefore authentic and correct." From The Engineer 1925/06/05 by Walter Laidlaw.
1843 Transferred to the new works at Crewe as Locomotive Superintendent
1844 He Married Mary Ewart (1819-1889)
1846 The GJR became part of the London and North Western Railway
1851 Living at Chester Street, Monks Coppenhall, (age 38 and born at Truro), Engineer. Living with wife Mary (age 29 and born at Newcastle-upon-Tyne) and sons Richard (age 5), Robert (age 2) and Francis (age 9 months) and daughter Jane (age 4). Plus a servant. 
His son, Arthur Reginald Trevithick, worked for many years on the LNWR, including several years as assistant locomotive works manager at Crewe.
Another son, Frederick Harvey Trevithick, worked for both the Great Western and the Egyptian State Railways and at the latter advanced to Chief Mechanical Engineer
1857 He resigned from the LNWR
After leaving the LNWR he returned to Cornwall and became factor of the Tehidy estates, of which his Grandfather had been mineral agent in the 18th century.
1872 He wrote a 'Life of Richard Trevithick' and had it published.
1877 Age 65. He died at Penzance on 27 October 1877 and was buried there.
The following was taken from the The Engineer 1877/11/02.
'Eldest son of the celebrated Richard Trevithick, the apostle of high-pressure steam. Mr. Francis Trevithick wrote a biography of his father, which is full of interesting matter; he took an important part in the railway world in its early days. He died at Penzance on the 27th of October, aged sixty-five, and will be interred today in the Penzance cemetery.'
Sources of Information
- 1851 Census
-  Wikipedia