The reversed-L plan of the Millwall Docks is a truncated version of the inverted-T plan projected in 1863 as a 350ft-wide ‘canal’. The dimensions and particulars of the built section of docks had been settled by (Sir) John Fowler and William Wilson by July 1865 when (Sir) John Kelk and John Aird & Son began the excavation work.
There were extensive tramways and two pumping steam engines on the south side of the estate to drain the works. Excavation was relatively easy because the land was low, generally about 10ft below high water, and the spoil could be used on site to raise the level of the quays.
There were 2,000 to 3,000 labourers at work, reportedly well organized, and progress was rapid. Work on the concrete-and-brick dock walls had started by the beginning of 1866. In January 1867 the walls of the Outer Dock were coped, and the Inner Dock was well advanced. The docks were completed, with the quays of the Outer Dock levelled, in July 1867. The eastern end of the Outer Dock near East Ferry Road was an unwalled bank, as an extension eastwards remained a possibility.