 1n 1902, Mott formed what turned out to be a lifelong partnership with another protégé of Baker's, David Hay.Subsequently, the partnership of Mott and Hay (now Mott MacDonald) worked on extending the Central London Railway, the building of escalators in London Underground and the construction of the Tyne and Southwark Bridges.It also designed the underpinning required to stabilise Clifford's Tower in York.