Millennium Bridge, London people walking caused small sideways oscillations in the bridge, which in turn caused people on the bridge to sway in step, increasing the amplitude of the bridge oscillations and continually reinforcing the effect. On the day of opening, the bridge was crossed by 90,000 people, with up to 2,000 on the bridge at any one time. Resonant vibrational modes due to vertical loads (such as trains, traffic, pedestrians) and wind loads are well understood in bridge design. In the case of the Millennium Bridge, because the lateral motion caused the pedestrians loading the bridge to directly participate with the bridge,
London Bridge City of London placed the bridge on the market and began to look for potential buyers. Council member Ivan Luckin had put forward the idea of selling the bridge, and recalled: "They all thought I was completely crazy when I suggested we should sell London Bridge when it needed replacing." On 18 April 1968, Rennie's bridge was purchased by the Missourian entrepreneur Robert P. McCulloch of McCulloch Oil for US$2,460,000. The claim that McCulloch believed mistakenly that he was buying the more impressive Tower Bridge was denied by Luckin in a newspaper interview. As the bridge was taken apart, each