[2] After graduating, in October 1876 he was apprenticed to railway engineer Robert Pearson Brereton who was responsible for completing many of Isambard Kingdom Brunel's projects after his death in 1859.

[4][5] Cruttwell was only with Brereton until 1878 (or 1879)[5] when he joined the firm of Sir John Wolfe Barry and Henry Marc Brunel.

But aged 25 he was appointed resident engineer responsible for the construction of Blackfriars Railway Bridge, a role he held between 1883 and 1886.

[7] Cruttwell chose Tower Bridge and it was in this role he achieved national prominence as the engineer in charge of its construction[8][9][10] from its inception in 1886 to its opening on 30 June 1894.

"[13] In 1898, after working for Wolfe Barry and Brunel for 16 years, Cruttwell was nominated to become a member of the Institution of Mechanical Engineers; Brunel summarised Cruttwell's career to that year:"[He was educated] at King's College, London (Applied Science Department) from 1874 to 1876... From 1878 to 1894, Cruttwell was employed continuously by Mr (later Sir) John Wolfe Barry and Mr Henry Marc Brunel initially in their office, then in sole charge as resident engineer at Blackfriars Railway Bridge from 1883 to 1886, and then at the Tower Bridge from 1886 to 1894.

"[19] Retaining the role of consulting engineer to Tower Bridge (a position he held until he died in 1933),[3] Cruttwell went into independent practice at 14 Delahay Street, Westminster, in 1897.

[24] (A second competition in 1902 was won by Selfe but construction of his design never started due to an economic slowdown and a 1904 change of government.

[12] Cruttwell's expertise on bridges, docks and rivers would be called on more widely, and nationally, for engineering projects not designed by him or his firm.

[31] Later that year, in November, he was tasked with providing an independent expert assessment to assist in an arbitration case regarding the Royal Edward Dock in Avonmouth.

[33] In 1913, Cruttwell, with John and K A Wolfe Barry and Lyster, was commissioned to report on "'dockizing' the navigable Cut" at Neath Harbour.

In 1911, his main residence was Bayfield House, Little Bookham, near Leatherhead in Surrey, a substantial property with 45 acres and 15 bedrooms.

[4] From there he moved to Fox Mead, also in Little Bookham, and he would die in a nearby cottage called Rosemary in Clinton Road, Leatherhead.

[43] By 1927 he had the 2024 equivalent of around £5 million and owned several properties, but he lost most of his fortune (held in railway shares) during the Great Depression.