In the 1820s Donkin became a director of the Thames Tunnel Company, having become acquainted with Marc Brunel when he had supplied equipment for his machinery at Chatham Dockyard.
In 1825–27 Donkin supplied pumps for removing water from the tunnel and also workmen for modifying the tunnelling shield; at one time it was even suggested that he replace Brunel as engineer.

In 1826 he constructed a model of a landing stage proposed by Brunel for use at Liverpool.

Donkin's works regularly supplied machinery for use in civil engineering projects, including dredging machines for the Caledonian Canal in 1816, the Prussian Government in 1817, the Göta Canal (Sweden) in 1821, and the Calder and Hebble Navigation in 1824.
Stationary steam engines were also supplied for use in the construction of the locks on the Caledonian Canal.

As an eminent engineer, Donkin was often consulted on civil engineering matters.
He supported Thomas Telford's 1814 proposals for a massive suspension bridge at Runcorn, and in 1821 reported along with Henry Maudslay on an iron bridge erected by Ralph Dodd at Springfield, Chelmsford.
Thomas Telford employed Donkin in his survey of rivers in the London area for the Water Supply report, completed shortly before Telford's death.
Donkin died in 1855 and was buried in a family plot in Nunhead Cemetery, south London.
In the 1820s Donkin became a director of the Thames Tunnel Company, having become acquainted with Marc Brunel when he had supplied equipment for his machinery at Chatham Dockyard. In 1825–27 Donkin supplied pumps for removing water from the tunnel and also workmen for modifying the tunnelling shield; at one time it was even suggested that he replace Brunel as engineer.
In 1826 he constructed a model of a landing stage proposed by Brunel for use at Liverpool.
Donkin's works regularly supplied machinery for use in civil engineering projects, including dredging machines for the Caledonian Canal in 1816, the Prussian Government in 1817, the Göta Canal (Sweden) in 1821, and the Calder and Hebble Navigation in 1824. Stationary steam engines were also supplied for use in the construction of the locks on the Caledonian Canal.
As an eminent engineer, Donkin was often consulted on civil engineering matters. He supported Thomas Telford's 1814 proposals for a massive suspension bridge at Runcorn, and in 1821 reported along with Henry Maudslay on an iron bridge erected by Ralph Dodd at Springfield, Chelmsford. Thomas Telford employed Donkin in his survey of rivers in the London area for the Water Supply report, completed shortly before Telford's death. Donkin died in 1855 and was buried in a family plot in Nunhead Cemetery, south London.
Bryan Donkin