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 Is Falling Down Dancing o'er The Lady-Lee. </poem> The oldest extant version could be that recalled by a correspondent to the "Gentleman's Magazine" in 1823, which he claimed to have heard from a woman who was a child in the reign of Charles II (r. 1660–85) and had the lyrics: <poem>London Bridge is broken down, London Bridge is broken down, The earliest printed English version is in the oldest extant collection of nursery rhymes, "Tommy Thumb's Pretty Song Book", printed by John Newbery in London (c. 1744), beginning with the following text: <poem> London Bridge Is Broken down, Dance over my Lady Lee.