The firm also advised on proposals for underground railways in Sydney, Africa and Russia. David Anderson was made a partner in 1920 after returning from army service. The firm was thereafter known as Mott, Hay and Anderson. During the 1920s, it designed the rolling bridge over the River Dee at Queensferry, the Tyne Bridge in Newcastle and the Trent Bridge in Nottingham. It also designed the enlargement of the City & South London Railway tunnels and their extension past Camden Town and Clapham South to form the Northern Line of London Underground.