1840 William Mackenzie and Thomas Brassey began railway works in France, and elsewhere. These included the greater part of the Paris and Rouen Railway; the whole of the Rouen and Havre Railway, including the stations and the maintenance of way of both lines; the line from Rouen to Dieppe, all under Joseph Locke, and George Neumann. Also part of the Amiens and Boulogne line and the canal works at Bar le Duc; and the Orleans, Tours, and Bordeaux contract.
1841 Contractors for the Paris to Rouen railway, and a canal connecting the Rhone and the Marne
Also see Brassey, Mackenzie and Stephenson
c.1843 John Stephenson and Co in association with William Mackenzie and Thomas Brassey, offered James Falshaw the charge of the construction of the Lancaster and Carlisle Railway, the contract for which, as a single line, had been taken by the firm.
Mackenzie and Brassey, in conjunction with John Stephenson, constructed the whole of the lines from Lancaster to Edinburgh and Glasgow, under Mr. Locke and John Edward Errington, with their numerous tributary branches and extensions, the Scottish Central to Perth, and the Scottish Midland to Forfar.