When work began on London Underground's Victoria line in the early 1960s, responsibility for the tunnelling works was split between Mott, Hay and Anderson and Sir William Halcrow and Partners, each acting as Engineer for approximately half the length of the line. MHA partner John Bartlett patented the bentonite-slurry shield tunnel boring machine (UK patent 1083322) and a trial length of tunnel was drilled successfully through poor ground conditions at New Cross in London. The slurry shield design paved the way for the earth pressure balance TBM commonly used today.